fix: don't show loading state when empty completer array is provided

[akoreman]

Issue #, if available: NA

Description of changes: Currently, when providing an empty completer array, we show the popup with the completion loading state indefinitely:

Screen.Recording.2023-12-08.at.16.07.43.mov

This adds a check for the completer length in the showing of the loading popup.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (aac600d) 87.59% compared to head (7e08bf5) 87.60%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5418   +/-   ##
=======================================
  Coverage   87.59%   87.60%           
=======================================
  Files         583      583           
  Lines       46389    46397    +8     
  Branches     7018     7019    +1     
=======================================
+ Hits        40636    40644    +8     
  Misses       5753     5753           

Flag	Coverage Δ
unittests	87.60% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.