Created attachment 123509 [details]
Screenshot showing the issue.

SUMMARY
In the window that allows us to configure notifications per-application, typing a search query in the sidebar and then clearing it does not update the sidebar properly.

STEPS TO REPRODUCE
1. Open the notification settings and go to 'configure applications'
2. Type a query in the searchbox which matches some item (eg. 'acc')
3. Clear the searchbox by clicking the 'clear' button
4. Note that some items in the 'system services' section have the same name as those in the 'applications' section.
5. Click one of the duplicated items in the 'system services' section.
6. Note that the main area shows the configuration for the system service which should've been in the location you were clicking, and not the erroneously duplicated label (see attached screenshot)
7. Typing a query that doesn't match anything (eg. 'asdf') in the searchbox and clearing seems to fix this till the next occurrence.

OBSERVED RESULT
Item names in the sidebar don't get updated properly when the query is cleared.

EXPECTED RESULT
Item names should get updated properly when the search query is cleared.

SOFTWARE/OS VERSIONS
Linux distro: Arch Linux
KDE Plasma Version: 5.17.1
KDE Frameworks Version: 5.63.0
Qt Version: 5.13.1