Steps to reproduce:

1. Open any project
2. Click the lower portion of the expand/collapse triangle icon of a project folder and observe that the folder does not expand or collapse (the folder does get selected even though it doesn't register the expand/collapse)
3. Click above the expand/collapse triangle icon of a project folder and observe that the folder does get expanded or collapsed even though you are not clicking on the triangle.

See attached video "case_718844-Unity_Bug_-_Expander_Hitbox_Offset.mov" for demonstration of the issue.