Problem/Bug My server keeps crashing: Exception ticking world

Here is the primary error. The server crashes and I receive this error a few seconds after a player joins the server.

Code:

---- Minecraft Crash Report ----
// My bad.

Time: 6/22/19 12:20 PM
Description: Exception ticking world

java.lang.NullPointerException: Exception ticking world
    at net.minecraft.server.v1_13_R2.ChunkTaskScheduler.a(ChunkTaskScheduler.java:101)
    at net.minecraft.server.v1_13_R2.ChunkProviderServer.unloadChunks(ChunkProviderServer.java:303)
    at net.minecraft.server.v1_13_R2.WorldServer.doTick(WorldServer.java:268)
    at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:952)
    at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417)
    at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:831)
    at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:729)
    at java.lang.Thread.run(Unknown Source)

Can anyone help fix this?
Edit: I know for a fact it is not caused by a plugin.
Edit 2: It only happened with me and deleting playerdata in the world fixes it.