[BUG] "arc config edit -g" reports error

[Martin-Kuhl]

Describe the bug
Although the operation works, setting general.gitname or general.gitemail in the ARC Commander config using arc config edit -g reports an error when these fields were not present before,

To Reproduce

1. Open the ARC Commander
2. Run arc config edit -g
3. Remove fields general.gitname and general.gitemail if present and close the editor
4. Run arc config edit -g again
5. Add the mentioned fields and information

Expected behavior
Instead of reporting an error, the AC should rather report that the mentioned fields were added or changed.