fix(modal): parent page invalid hierarchy handling [extended]

[vakrilov]

Extension of #5841:

• Added "report error and return immediately logic" _showNativeModalView in _hideNativeModalView
• getParentWithViewController refactor to be more concise
• guard in showUIAlertController method

CC @NathanWalker

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• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/WritingUnitTests.md.

What is the current behavior?

Apps break with the current throw without any effective way to handle. Additionally a while loop was being used without safe guards to prevent undefined access.

What is the new behavior?

With tracing on, developers can now properly debug their apps for various use cases without an untested (and most often not reproducible) ux flow/interaction hitting production resulting in this throw leaving the app unstable and unpredictable. Also proper safe guards have been added to prevent undefined access.

[vakrilov]

It's highly unlikely that the parent is undefined here as it's only called _closeModalCallback where it is scoped. Guard it and viewController prop access anyway.

[vakrilov]

test

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.