Crop tool sanity-checks its GSettings: Closes #7359
Crop tool sanity-checks its GSettings: Closes #7359

In the ticket, the user's last-chosen crop setting was a separator,
leading to havoc.

abrauchli/shotwell,ritchiewilson/shotwell,abrauchli/shotwell,ritchiewilson/shotwell,ritchiewilson/shotwell,jimbonator/shotwell,jimbonator/shotwell,jimbonator/shotwell,abrauchli/shotwell