Added test for connect_list_selection and fix remaining PyQt6 issue

[astrofrog]

Somehow I had not added a test for connect_list_selection - this also fixes a PyQt6 issue from code now covered by new test

[codecov]

Codecov Report

Base: 94.28% // Head: 96.65% // Increases project coverage by +2.37% 🎉

Coverage data is based on head (46139f2) compared to base (cf80544).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   94.28%   96.65%   +2.37%     
==========================================
  Files          16       17       +1     
  Lines        2098     2182      +84     
==========================================
+ Hits         1978     2109     +131     
+ Misses        120       73      -47     

Impacted Files	Coverage Δ
echo/qt/connect.py	88.78% <100.00%> (+15.06%)	⬆️
echo/qt/tests/test_connect_list_selection.py	100.00% <100.00%> (ø)

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