Ticking

Hi
I loaded minecraft, and then after 2 mins, it crashes with this error

The game crashed whilst exception ticking world
Error: java.lang.IllegalArgumentException: Cannot set property class_2746

{name=snowy, clazz=class java.lang.Boolean, values=[true, false]}

as it does not exist in Block

{more_slabs_stairs_and_walls:grass_block_wall}