So, I wanted to customize this mod a little, but it went wrong

I've downloaded source for 1.19 and even if I dont change anything and build, I get leaf decaying on every tree except vanilla.

Any tips how to fix that? (I tried to find something on issues, but didn't find anything, which could help me)

Did you run data generation using ./gradlew runDatagen?

no, I'm new to mod developping, I'll try

yeah, that helped, thank you so much