fix: the toolbar will be blocked if the scroll bar is hidden

[LucasXu0]

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 73.27%. Comparing base (8b9ccf8) to head (c06cb9e).

Files	Patch %	Lines
...b/src/editor/toolbar/mobile/mobile_toolbar_v2.dart	0.00%	11 Missing ⚠️
...toolbar/mobile/utils/keyboard_height_observer.dart	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #839      +/-   ##
==========================================
- Coverage   73.38%   73.27%   -0.11%     
==========================================
  Files         315      315              
  Lines       14584    14588       +4     
==========================================
- Hits        10702    10689      -13     
- Misses       3882     3899      +17     

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