When DigiKam has scanned an album and found images, and then those images are deleted from the folder from outside DigiKam, then the database still keeps the entry. Rebuilding the thumbnails does nothing to rid the database of the entry. The only way to do this with out editing the database directly, is to remove the album and re-add it but that's not very efficent.

Reproducible: Always

Steps to Reproduce:
1. Scan an album.
2. Close DigiKam 
3. Open File system and delete an image from the scanned album directly.
4. Start DigiKam again and view the album. The thumbnail is still there but, the file behind it is no longer available.
5. Attempting to delete the thumbnail from DigiKam now throws an error that the file doesn't exist, but the thumbnail is still present.
6. Rebuild the thumbnails for the album. Afterward the thumbnail is gone but there is still a square showing where it should be and the entry is still there.


Expected Results:  
Either, when I attempt to delete the thumbnail, and the file is no longer present then the thumbnail should be removed as well, or when I rebuild the thumbnails for the album and the file is no longer present then the entry should be removed from the database.