When you delete something starting from a list page, a card page opens and an error occurs, this error message is in the background. E.g.
- The page has an error. Correct the error or try to revert the change.
- The Assembly Line cannot be deleted when a related Warehouse Activity Line exists.

It would be nice if this error message was also displayed instead of "There are unsaved changes on the page. Do you want to discard these changes?".