When date format is deleted/updated, date format type is not updated.

Took me quite a while to figure this, but the date format type is stored in a variable, but not as an id pointing to date_format table, but rather the format itself. When updating/deleting the date format (if custom), this variable is not changed. When visiting date format type settings, it all seems ok because since the format is not on the select list, the format type seems to be using the first format while that's not what's really happening. Workaroud is saving this same settings page.