Minecraft version: 1.12.2
Wizardry version: 4.3.2
Environment: Singleplayer

Issue details:

This crash happened while just running around the world. I have a few other mods installed, but it seems like biomesoplenty and wizardry is at fault here.

Other mods involved: Biomes o Plenty

Link to crash report: Pastebin does not work for me, so I attached it as a separate file.
crash-2021-01-04_01.22.59-server.txt

After further investigation it seems to happen when a wizard shoots a mob but the projectile hits a blade of BOP grass.

Can confirm this issue, took my entire dedicated server out.

Seems to happen with version 4.3 and beyond but it seems fine for older versions

Appears to occur on this line when calling isReplaceable. In both my crash and the OP's, it seems that the target block at pos.up() is an air block. A possible fix would be checking that this block is not air before checking isReplaceable?

Seems to be similar to #519, but that got fixed in 4.3... hmmm....