I just noticed this error in my server logs and am not sure what is happening:

[11:31:15] [Server thread/FATAL] [VanillaFix]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_351]
at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_351]
at net.minecraft.util.Util.runTask(SourceFile:531) [h.class:?]
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:840) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:461) [nz.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:778) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:624) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_351]
Caused by: java.lang.NullPointerException