The Basalt brick slabs appear to be crashing my server. I got this error:

java.lang.IllegalArgumentException: Cannot get property PropertyEnum{name=half, clazz=class net.minecraft.block.BlockSlab$EnumBlockHalf, values=[top, bottom]} as it does not exist in BlockStateContainer{block=quark:stone_basalt_bricks_slab_double, properties=[prop]}

Here is the Crash Log

Report this to CustomSpawner. The mod needs to check if the property exists.