I used forge-2778
When I don't add this mod, everything is fine, and when I do it will prompt an error report. It is possible that the monster can pick up the square, place the square, destroy the entity error caused by the square.

Description: Exception in server tick loop

java.lang.NullPointerException: Exception in server tick loop

at net.minecraft.world.WorldEntitySpawner.func_77191_a(WorldEntitySpawner.java:417)

at net.minecraft.world.gen.ChunkGeneratorOverworld.func_185931_b(ChunkGeneratorOverworld.java:466)

at net.minecraft.world.chunk.Chunk.func_186034_a(Chunk.java:1019)

at net.minecraft.world.chunk.Chunk.func_186030_a(Chunk.java:999)

at net.minecraft.world.gen.ChunkProviderServer.func_186025_d(ChunkProviderServer.java:157)

at net.minecraft.server.MinecraftServer.func_71222_d(MinecraftServer.java:344)

at net.minecraft.server.integrated.IntegratedServer.func_71247_a(IntegratedServer.java:186)

at net.minecraft.server.integrated.IntegratedServer.func_71197_b(IntegratedServer.java:209)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:486)

at java.lang.Thread.run(Unknown Source)

i need more info: mod version, full crashlog and not only a part of it

is this still relevant?

closed since no answer in such a long time