Fixed some Errors

Changelog:

• solve the problem, that non humanlike pawns throw an error by ManualPawnList Gizmo
• Only show the ManualPawnList Gizmo, when it has an effect.

All Infos in the Readme.md https://github.com/AllenCaine/DoNotCutTrees

How to Install:
Download the DoNotAutoCutTrees_v1.2.zip and unzip it in your RimWorld mod folder.
More Infos: https://rimworldwiki.com/wiki/Installing_mods