Fix: Always call Flutter.onError

[ueman]

📜 Description

See motivation

💡 Motivation and Context

Closes #522

💚 How did you test it?

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• I updated the docs if needed
• All tests passing
• No breaking changes

🔮 Next steps

[codecov-commenter]

Codecov Report

Merging #533 (b75202e) into main (d5416f8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #533   +/-   ##
=======================================
  Coverage   91.54%   91.54%           
=======================================
  Files          74       74           
  Lines        2426     2426           
=======================================
  Hits         2221     2221           
  Misses        205      205           

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