QML projects silently fail to load if they don't contain at least 1 ".UI.QML" file

I have a project containing many QML files, but only one .UI.QML file. (What is the .UI.QML even used for? They are useless, because they can't have scripts in them?)

If I delete the last .UI.QML file, my project silently fails to load in QTDS 4.0. I literally cannot even load the project into the editor, it just silently fails. Other projects load & run fine.

If I put the .UI.QML file back, everything works fine, but it defaults (annoyingly) to loading that .UI.QML every time I open the project. It would be good if this was fixed and it loaded the same set of files as last time when I open the project. Some people might abandon the editor as broken permanently if they are not smart enough to figure out what is causing this bad behaviour But I love QTDS 4.0.