The game crashed whilst unexpected error Error: java.lang.NullPointerException: Unexpected error

[Itz_Chroma_]

Hello, im trying to play 5b5t.org (anarchy server) with inertia client 3.1.3 client using forge 1.12.2 but when i try to join in the server my game just crashes 
and go like "The game crashed whilst unexpected error Error: java.lang.NullPointerException: Unexpected error" 
 

[Itz_Chroma_]

and when i try to load a world that message shows up "The game crashed whilst exception in server tick loop Error: java.lang.IllegalArgumentException: ChunkNibbleArrays should be 2048 bytes not: 0"