[geolocator_apple] Crash if listen/cancel is executed in quick succession

[mkurz-it]

The onDidAuthorizationChanged is executed by iOS somewhen afer CLLocationManager is created in onListenWithArguments.

If the the subscription is canceled in the meantime _eventSink (onCancelWithArguments) is set to nil leading to accessing _eventSink when already nil (BAD_ACCESS crash).

Pre-launch Checklist

• I made sure the project builds.
• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is does not need version changes.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I rebased onto main.
• I added new tests to check the change I am making, or this PR does not need tests.
• I made sure all existing and new tests are passing.
• I ran dart format . and committed any changes.
• I ran flutter analyze and fixed any errors.

[TimHoogstrate]

Dear @mkurz-it,

Thanks for your contribution. Is there an issue related to this PR? I tried to reproduce this in "main" but I could not make it crash (although I can see that it potentially could crash from code :)).

Kind regards

[mkurz-it]

Hi @TimHoogstrate

Thanks for taking your time.

... Is there an issue related to this PR? I tried to reproduce this in "main" but I could not make it crash (although I can see that it potentially could crash from code :)).

There is no open issue. We are using your package in our APP and it crashed.
When analyzing the problem the fixed code was the cause.

FYI: It did not crash on every startup (so every 5-10 starts).
It will crash if you cancel the subscription quickly after subscription.
Actually before iOS called onDidAuthorizationChanged (is called asynchronously by the OS).

Best regards,

Michael

[TimHoogstrate]

Dear @mkurz-it,

It looks good, but can you "split/update" the PR in geolocator_apple and remove/revert the "geolocator" App Facing Package changes, as they are not needed. It will be updated automatically as a patch to users. If you need some help, ping us.

Kind regards,