Double click cannot unstage files

When the 'stage files on double click' option is enabled, you can double click to stage files, but can not double click them again to unstage. The latest update broke this expected behavior.

Steps to repro:

1. Go to Preferences > Git
2. Check "Stage files on double click"
3. Double click a staged file (it should move into staging)
4. Double click the staged file

Expected:
The file should move back to "Unstaged files"

Actual:
Nothing happens