Description of the need In rich text editor in image details, users are allowed to click the insert or update button even if they do not have a file chosen.
Proposed solution You could block the "Update" button until an image is added or have a popup to notify the user that they do not have an image selected when clicking insert/update.
Additional information
Inserting an non-existent file:

Updating after a file is removed:

Recent comments
There is a Drupal 7 contrib module that "lets the administrator see all administration pages in her preferred language" and which could be ported to Backdrop: https://www.drupal.org/project/...
Allow admin to select admin language seperate from front end language (multilingual)
@stpaultim – You're right: my approach affects also the main menu. I guess, because menus are also considered as user interface (not as content). @findlabnet – If I didn't miss anything,...
Allow admin to select admin language seperate from front end language (multilingual)
Go to the account edit of the desired user. On the horizontal tab below "Region and Language," select "English" or another language. WFM.
Allow admin to select admin language seperate from front end language (multilingual)