Backend: Respect minecraft nullability in more places

[CalMWolfs]

What

Fix code in a bunch of spots that technically could cause an npe because the methods are nullable just MC 1.8.9 doesnt mark them as such. This fixes preprocessing for future versions where these methods are marked as nullable and will show as an error in the code

Errors for preprocessing 1.8.9 -> 1.12.2 reduced by 31

Changelog Technical Details

• Updated more parts of the code to respect Minecraft's nullability. - CalMWolfs

[github-actions[bot]]

This pull request has conflicts with the base branch "beta". Please resolve those so we can test out your changes.

[github-actions[bot]]

Conflicts have been resolved! 🎉