If you place a flowering rush on a moss block, with a slab above it (river slab in this case), it crashes the game instead of simply just not placing the flowering rush there.

Photo below of the location, if it helps! And also, a paste of my crash log. Cheers!

Dunno if any of my mods conflict, but feels alright to report anywho.

https://pastebin.com/r3hZXvDQ