Auto-Type: Only match non-empty associations

[hifi]

Previously empty associations matched any window but since you can use a wildcard (*) if you specifically want that this change makes it possible to define multiple sequences for the global search if you need to.

Additionally show empty associations in the list as "(empty)" to better differentiate between rows if no title is set.

This trivial change makes #6869 possible without touching the dialog code.

Screenshots

Testing strategy

Manually on Linux.

Type of change

• ✅ New feature (change that adds functionality)
• ✅ Breaking change (causes existing functionality to change)

[codecov-commenter]

Codecov Report

Merging #7391 (530d023) into develop (86ba58d) will decrease coverage by 0.01%.
The diff coverage is 66.67%.

❗ Current head 530d023 differs from pull request most recent head 17fe36f. Consider uploading reports for the commit 17fe36f to get more accurate results

@@             Coverage Diff             @@
##           develop    #7391      +/-   ##
===========================================
- Coverage    64.33%   64.32%   -0.01%     
===========================================
  Files          339      339              
  Lines        43195    43197       +2     
===========================================
- Hits         27787    27785       -2     
- Misses       15408    15412       +4     

Impacted Files	Coverage Δ
src/gui/entry/AutoTypeAssociationsModel.cpp	91.67% <50.00%> (-1.19%)	⬇️
src/core/Entry.cpp	82.55% <100.00%> (-0.20%)	⬇️
src/core/FileWatcher.cpp	85.54% <0.00%> (-1.20%)	⬇️

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[anantakrishna]

It seems that this documentation should have been changed as a part of this PR:

Leave the window title blank to offer additional default Auto-Type sequences, such as custom attributes.
— https://github.com/keepassxreboot/keepassxc/blob/develop/docs/topics/AutoType.adoc

If that's correct, I can try sending a PR for this. Please confirm.