Weird Crash

Lately I keep getting this weird crash after the server runs for awhile. No idea what it means or what could be causing it.

Was running 733 but updated to 739 after it happened a few times.

Code:

13:08:49 [SEVERE] java.lang.NullPointerException
13:08:49 [SEVERE]       at net.minecraft.server.EntityPainting.damageEntity(EntityPainting.java:209)
13:08:49 [SEVERE]       at net.minecraft.server.EntityArrow.p_(EntityArrow.java:178)
13:08:49 [SEVERE]       at net.minecraft.server.World.entityJoinedWorld(World.java:1007)
13:08:49 [SEVERE]       at net.minecraft.server.WorldServer.entityJoinedWorld(WorldServer.java:52)
13:08:49 [SEVERE]       at net.minecraft.server.World.playerJoinedWorld(World.java:989)
13:08:49 [SEVERE]       at net.minecraft.server.World.cleanUp(World.java:966)
13:08:49 [SEVERE]       at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:367)
13:08:49 [SEVERE]       at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:285)
13:08:49 [SEVERE]       at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)
13:08:49 [SEVERE] Unexpected exception
java.lang.NullPointerException
        at net.minecraft.server.EntityPainting.damageEntity(EntityPainting.java:209)
        at net.minecraft.server.EntityArrow.p_(EntityArrow.java:178)
        at net.minecraft.server.World.entityJoinedWorld(World.java:1007)
        at net.minecraft.server.WorldServer.entityJoinedWorld(WorldServer.java:52)
        at net.minecraft.server.World.playerJoinedWorld(World.java:989)
        at net.minecraft.server.World.cleanUp(World.java:966)
        at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:367)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:285)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)

The Plug-ins I am running:
AutoSave
BorderGuard
Craftbook
DeathTpPlus
General
NoCheat
Permissions
Vanish
WorldEdit
WorldGuard

My plugins are up to date, and the server has been fine for days (updated all my plugins a few days ago), but suddenly I get this crash, not sure what it means.

 

Update to the latest Recommended Build, currently b740. Though this issue should already be fixed in b739...