Java.lang.NullPointerException Help Me!!

Whenever I join my server it works fine but after a while is crashes and I need help!

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3
Time: 4/28/20 3:51 PM
Description: Exception in server tick loop
java.lang.NullPointerException: Exception in server tick loop
at org.bukkit.craftbukkit.libs.it.unimi.dsi.fastutil.longs.LongOpenHashSet$SetIterator.nextLong(LongOpenHashSet.java:464)
at net.minecraft.server.v1_14_R1.ChunkMapDistance$c.a(ChunkMapDistance.java:432)
at net.minecraft.server.v1_14_R1.ChunkMapDistance.a(ChunkMapDistance.java:94)
at net.minecraft.server.v1_14_R1.ChunkProviderServer.tickDistanceManager(ChunkProviderServer.java:245)
at net.minecraft.server.v1_14_R1.ChunkProviderServer.access$3(ChunkProviderServer.java:244)
at net.minecraft.server.v1_14_R1.ChunkProviderServer$a.executeNext(ChunkProviderServer.java:552)
at net.minecraft.server.v1_14_R1.ChunkProviderServer.runTasks(ChunkProviderServer.java:241)
at net.minecraft.server.v1_14_R1.MinecraftServer.aX(MinecraftServer.java:876)
at net.minecraft.server.v1_14_R1.MinecraftServer.executeNext(MinecraftServer.java:860)
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.executeAll(SourceFile:103)
at net.minecraft.server.v1_14_R1.MinecraftServer.sleepForTick(MinecraftServer.java:843)
at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:784)
at java.lang.Thread.run(Unknown Source)
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- System Details --
Details:
Minecraft Version: 1.14.4
Minecraft Version ID: 1.14.4
Operating System: Windows 10 (x86) version 10.0
Java Version: 1.8.0_251, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 6381680 bytes (6 MB) / 259522560 bytes (247 MB) up to 259522560 bytes (247 MB)
CPUs: 4
JVM Flags: 0 total;
CraftBukkit Information:
Running: CraftBukkit version git-Bukkit-3e3818b (MC: 1.14.4) (Implementing API version 1.14.4-R0.1-SNAPSHOT) true
Plugins: { ThunderPlus v1.0 me.fundy.thunderplus.Main [Fundy],}
Warnings: DEFAULT
Reload Count: 0
Threads: { RUNNABLE Signal Dispatcher: [], RUNNABLE Netty Server IO #2: [sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method), sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source), sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source), sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source), sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source), sun.nio.ch.SelectorImpl.select(Unknown Source), io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:756), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:411), io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884), java.lang.Thread.run(Unknown Source)], RUNNABLE Netty Server IO #0: [sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method), sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source), sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source), sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source), sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source), sun.nio.ch.SelectorImpl.select(Unknown Source), io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:756), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:411), io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884), java.lang.Thread.run(Unknown Source)], TIMED_WAITING ObjectCleanerThread: [java.lang.Object.wait(Native Method), java.lang.ref.ReferenceQueue.remove(Unknown Source), io.netty.util.internal.ObjectCleaner$1.run(ObjectCleaner.java:54), io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Unknown Source)], RUNNABLE Thread-4: [org.fusesource.jansi.internal.Kernel32.FillConsoleOutputCharacterW(Native Method), org.fusesource.jansi.WindowsAnsiOutputStream.processEraseLine(WindowsAnsiOutputStream.java:173), org.fusesource.jansi.AnsiOutputStream.processEscapeCommand(AnsiOutputStream.java:253), org.fusesource.jansi.AnsiOutputStream.write(AnsiOutputStream.java:125), java.io.FilterOutputStream.write(Unknown Source), sun.nio.cs.StreamEncoder.writeBytes(Unknown Source), sun.nio.cs.StreamEncoder.implFlushBuffer(Unknown Source), sun.nio.cs.StreamEncoder.implFlush(Unknown Source), sun.nio.cs.StreamEncoder.flush(Unknown Source), java.iutputStreamWriter.flush(Unknown Source), org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.flush(ConsoleReader.java:976), org.bukkit.craftbukkit.v1_14_R1.util.TerminalConsoleWriterThread.run(TerminalConsoleWriterThread.java:38)], WAITING Reference Handler: [java.lang.Object.wait(Native Method), java.lang.Object.wait(Unknown Source), java.lang.ref.Reference.tryHandlePending(Unknown Source), java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)], RUNNABLE DestroyJavaVM: [], RUNNABLE Attach Listener: [], RUNNABLE Netty Server IO #1: [sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method), sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source), sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source), sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source), sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source), sun.nio.ch.SelectorImpl.select(Unknown Source), io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:756), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:411), io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884), java.lang.Thread.run(Unknown Source)], WAITING Server-Worker-12: [sun.misc.Unsafe.park(Native Method), java.util.concurrent.ForkJoinPool.awaitWork(Unknown Source), java.util.concurrent.ForkJoinPool.runWorker(Unknown Source), java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)], TIMED_WAITING Server Infinisleeper: [java.lang.Thread.sleep(Native Method), net.minecraft.server.v1_14_R1.DedicatedServer$1.run(DedicatedServer.java:68)], TIMED_WAITING Timer-0: [java.lang.Object.wait(Native Method), java.util.TimerThread.mainLoop(Unknown Source), java.util.TimerThread.run(Unknown Source)], RUNNABLE Server thread: [java.lang.Thread.dumpThreads(Native Method), java.lang.Thread.getAllStackTraces(Unknown Source), org.bukkit.craftbukkit.v1_14_R1.CraftCrashReport.call(CraftCrashReport.java:33), net.minecraft.server.v1_14_R1.CrashReportSystemDetails.a(SourceFile:79), net.minecraft.server.v1_14_R1.CrashReport.h(CrashReport.java:71), net.minecraft.server.v1_14_R1.CrashReport.<init>(CrashReport.java:35), net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:799), java.lang.Thread.run(Unknown Source)], TIMED_WAITING Server-Worker-11: [sun.misc.Unsafe.park(Native Method), java.util.concurrent.ForkJoinPool.awaitWork(Unknown Source), java.util.concurrent.ForkJoinPool.runWorker(Unknown Source), java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)], RUNNABLE Server console handler: [org.fusesource.jansi.internal.Kernel32.ReadConsoleInputW(Native Method), org.fusesource.jansi.internal.Kernel32.readConsoleInputHelper(Kernel32.java:761), org.fusesource.jansi.internal.Kernel32.readConsoleKeyInput(Kernel32.java:794), org.fusesource.jansi.internal.WindowsSupport.readConsoleInput(WindowsSupport.java:97), org.bukkit.craftbukkit.libs.jline.WindowsTerminal.readConsoleInput(WindowsTerminal.java:215), org.bukkit.craftbukkit.libs.jline.WindowsTerminal.access$000(WindowsTerminal.java:55), org.bukkit.craftbukkit.libs.jline.WindowsTerminal$1.read(WindowsTerminal.java:157), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:169), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:137), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:246), org.bukkit.craftbukkit.libs.jline.internal.InputStreamReader.read(InputStreamReader.java:261), org.bukkit.craftbukkit.libs.jline.internal.InputStreamReader.read(InputStreamReader.java:198), org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.readCharacter(ConsoleReader.java:2145), org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.readLine(ConsoleReader.java:2349), net.minecraft.server.v1_14_R1.DedicatedServer$2.run(DedicatedServer.java:94)], WAITING NonBlockingInputStreamThread: [java.lang.Object.wait(Native Method), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.run(NonBlockingInputStream.java:278), java.lang.Thread.run(Unknown Source)], WAITING Server Watchdog: [java.lang.Object.wait(Native Method), java.lang.Thread.join(Unknown Source), java.lang.Thread.join(Unknown Source), java.lang.ApplicationShutdownHooks.runHooks(Unknown Source), java.lang.ApplicationShutdownHooks$1.run(Unknown Source), java.lang.Shutdown.runHooks(Unknown Source), java.lang.Shutdown.sequence(Unknown Source), java.lang.Shutdown.exit(Unknown Source), java.lang.Runtime.exit(Unknown Source), java.lang.System.exit(Unknown Source), net.minecraft.server.v1_14_R1.ThreadWatchdog.a(SourceFile:91), net.minecraft.server.v1_14_R1.ThreadWatchdog.run(SourceFile:71), java.lang.Thread.run(Unknown Source)], WAITING Finalizer: [java.lang.Object.wait(Native Method), java.lang.ref.ReferenceQueue.remove(Unknown Source), java.lang.ref.ReferenceQueue.remove(Unknown Source), java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)], RUNNABLE Thread-3: [sun.misc.Unsafe.defineAnonymousClass(Native Method), java.lang.invoke.InnerClassLambdaMetafactory.spinInnerClass(Unknown Source), java.lang.invoke.InnerClassLambdaMetafactory.buildCallSite(Unknown Source), java.lang.invoke.LambdaMetafactory.metafactory(Unknown Source), java.lang.invoke.LambdaForm$DMH/15360108.invokeStatic_L6_L(LambdaForm$DMH), java.lang.invoke.LambdaForm$BMH/5197290.reinvoke(LambdaForm$BMH), java.lang.invoke.LambdaForm$MH/30440635.invoke_MT(LambdaForm$MH), java.lang.invoke.CallSite.makeSite(Unknown Source), java.lang.invoke.MethodHandleNatives.linkCallSiteImpl(Unknown Source), java.lang.invoke.MethodHandleNatives.linkCallSite(Unknown Source), net.minecraft.server.v1_14_R1.PlayerChunkMap.save(PlayerChunkMap.java:301), net.minecraft.server.v1_14_R1.ChunkProviderServer.save(ChunkProviderServer.java:295), net.minecraft.server.v1_14_R1.WorldServer.save(WorldServer.java:770), net.minecraft.server.v1_14_R1.MinecraftServer.saveChunks(MinecraftServer.java:637), net.minecraft.server.v1_14_R1.MinecraftServer.stop(MinecraftServer.java:707), net.minecraft.server.v1_14_R1.DedicatedServer.stop(DedicatedServer.java:668), net.minecraft.server.v1_14_R1.MinecraftServer.close(MinecraftServer.java:658), org.bukkit.craftbukkit.v1_14_R1.util.ServerShutdownThread.run(ServerShutdownThread.java:15)], WAITING Server-Worker-9: [sun.misc.Unsafe.park(Native Method), java.util.concurrent.ForkJoinPool.awaitWork(Unknown Source), java.util.concurrent.ForkJoinPool.runWorker(Unknown Source), java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)], WAITING Snooper Timer: [java.lang.Object.wait(Native Method), java.lang.Object.wait(Unknown Source), java.util.TimerThread.mainLoop(Unknown Source), java.util.TimerThread.run(Unknown Source)],}
Recent tasks from 425-455{}
Force Loaded Chunks: { world: {}, world_nether: {}, world_the_end: {},}
Player Count: 0 / 20; []
Data Packs: vanilla, file/bukkit
Is Modded: Definitely; Server brand changed to 'CraftBukkit'
Type: Dedicated Server (map_server.txt)