Pontoon settings not accessible if profile has non existing locale as custom home page

[mathjazz]

This issue was created automatically by a script.

Bug 1725310

Bug Reporter: @flodolo
CC: @mathjazz

https://discourse.mozilla.org/t/i-cannot-open-my-settings/84380

Background: we used to have sat-Olck, which was removed as the team started using sat instead. At that point, the Settings page became impossible to access.

To fix it, I had to manually change the setting in Django admin. Not sure if we have other users in the same condition at this point.