[google_sign_in] Fix Exception leaking in debug mode (#64681)

[feinstein]

Description

This is related to flutter/flutter#26705 and many others. I already fixed this before on flutter/flutter#37343 submitting this PR #1937.

I am fixing this again.

Could the owners of these files make some sort of mechanism to avoid this from happening again?

---

I need some help with the tests, I honestly don't understand why the 'can sign in after init failed before' test is failing. For some reason the MockMethodCallHandler is only being called once. I didn't change anything on this test (just syntactic sugar, but it also fails if I remove it).

Related Issues

Fixes flutter/flutter#64681
Fixes flutter/flutter#45146

flutter/flutter#37343
flutter/flutter#26705
dart-lang/sdk#37268

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[feinstein]

@mehmetf could you help me figure out what's the problem with the tests?

[stuartmorgan-g]

All of the referenced issues are closed, referring to an issue that was recently fixed in the Dart VM. Given that, is this PR still necessary?

[stuartmorgan-g]

Thank you for your contribution. I'm going to close this PR for now since there are outstanding comments, just to get this off our PR review queue. Please don't hesitate to submit a new PR if you have the time to address the review comments. Thanks!

[feinstein]

Sorry Stuart, I forgot to reply... Yeah I don't think it's necessary anymore.