Bug 435343

(The "Component" should be something like People-album-Thumbnail)

SUMMARY
digiKam crashes (no more responding, kill process required) when opening a *People* album properties (Alt-Enter or right-click→Properties) if its Tag Thumbnail/Icon file was renamed (or moved) using filesystem (i.e. Windows Explorer - not a good practice but digKam should not crash). See also [1] Note below.

STEPS TO REPRODUCE
1. Assign a Tag Thumbnail to a People album using a face from gallery view
2. (info) digiKam can be kept open or closed now - does not change crash behaviour
3. Use Windows Explorer to rename or remove the previousy assigned Thumbnail file
4. Restart digiKam
5. On that Album, try getting its properties using Alt-Enter or right-click→Properties

OBSERVED RESULT
* digiKam is not responding to any mouse/keyboard input. End-Task fails and the process has to be killed.

EXPECTED RESULT
* digiKam to open the People album property interface/window.

SOFTWARE/OS VERSIONS
Windows: W10 (1909 on native hardware and 1809 on VMware player 15)
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
What I already tested:
* Crash on the released version 7.2.0 and also version 7.1.3 (3 Sep 2020) - no other versions tested.
* Does not happen using *Album* view Thumbnails (as opposed to *People* album)
* (info) If the Album Thumbnail file is restored to the same pathname, the icon just reappear (after digiKam restart) which in itself is a very useful feature to restore Thumbnails following path/file changed by mistake or without knowing this impact.

digiKam Options which may be relevant:
* Enabled setting: Settings → Configure → Collections → [X] Monitor the albums for external changes.
[1] Note that with this option enabled digiKam effectively detects a file rename from the file system and reflects this correctly in Properties (right-Tab) and Tool-Tip gallery view. It however seems not to "update/sync" the Album Thumbnail property.

(This is my 1st bug report, I am pleased to help, run additional tests, clarify as required. Thanks A LOT for this wonderfull open-source development, dayly used here).