[1.12.2] [Crash] World not loadable after removing villager professions

[Skaphegor]

I removed Open Blocks and the world was not loadable anymore. I detected that this was caused by GravestoneMod Extented not getting a villager profession. https://pastebin.com/qUyabbVT
I assume it writes a null in the world data or anywhere else.

The crash appears later shutting down the game. https://pastebin.com/0Sb7uxK3

See the full log.
2019-01-24-4.log

This also led to this issues. -> OpenMods/OpenBlocks#957 and XCompWiz/Mystcraft-Issues#335