If you have non-image files into a folder (.zip, .txt, etc.) DigiKam will not warn you when you will delete the folder. I agree DK is not expected to display these files, but still, I feel unsafe if it is able to delete a folder containing other files without at least warning me about them.

Reproducible: Always

Steps to Reproduce:
1. Create a folder under one of your collections
2. Open it with file explorer (Dolphin for me)
3. From the file explorer, create a text file
4. Back to DK, delete the folder

Actual Results:  
DK ask the usual question about deleting the folder itself, but don't warn about the text file, and when confirmed actually remove the folder.

Expected Results:  
DK should explicitly warn about the presence of this text file.

Fortunately, the text file is actually moved into the trash, and so it can be retrieved. But one may not check trash content very often...