Exception getting block type in world

[backfire51]

hi guys, i am getting this error whenever i try to start my minecraft forge server and i have no idea what's going on.

---- Minecraft Crash Report ----
// Don't do that.


Time: 13.1.26 10.58
Description: Exception getting block type in world


java.lang.NullPointerException
at net.minecraftforge.common.ForgeChunkManager.fetchDormantChunk(ForgeChunkManager.java:883)
at im.c(ChunkProviderServer.java:115)
at im.d(ChunkProviderServer.java:166)
at yc.e(World.java:524)
at yc.a(World.java:404)
at yc.c(World.java:433)
at yc.b(World.java:375)
at aaq.a(WorldProvider.java:100)
at in.b(WorldServer.java:775)
at in.a(WorldServer.java:739)
at yc.<init>(World.java:288)
at in.<init>(WorldServer.java:103)
at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:266)
at ho.c(DedicatedServer.java:180)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:458)
at fy.run(SourceFile:849)

[Cloudy]

Update to forge 511.