Internal Exception io.netty.handle.codec.DecoderException: java.lang.NullPointerException: Cannot invoke "na.b(String, int) becaus "☃" is null

this happen when i try to enter that a server upgrade form 1.17 pre2 to pre3 and got error
this server using datapack CavesAndCliffsPreview that was download form pre3 news website offcial