fix: don't detach completion popup while typing when prefix is empty

[akoreman]

Issue #, if available: NA

Description of changes: Currently, when auto showing completion during typing, the popup gets detached when the prefix is "". This can be problematic in situations when completions are coming in while typing sentences (e.g. when using AI code generation). When you pause after typing a space and a completion comes in from the completer, the popup will be detached because the prefix at that point in time is "".

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Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.56%. Comparing base (6e870fd) to head (95ad570).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5517   +/-   ##
=======================================
  Coverage   86.56%   86.56%           
=======================================
  Files         588      588           
  Lines       42553    42576   +23     
  Branches     7071     7071           
=======================================
+ Hits        36834    36858   +24     
+ Misses       5719     5718    -1     

Flag	Coverage Δ
unittests	86.56% <100.00%> (+<0.01%)	⬆️

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[andredcoliveira]

Looks good to me :)