Summary:
Calling `-[RCTRedBox showErrorMessage]` twice causes a crash
We used `-[UIViewController isBeingPresented]` to tell whether view controller is already presented.
But from the documentation:
> A Boolean value indicating whether the view controller is being presented.
Source: https://developer.apple.com/documentation/uikit/uiviewcontroller/2097564-beingpresented?language=objc#
---
So this means that if you present it, wait until presentation animation is finished and then call `-[RCTRedBox showErrorMessage]` again, following exception will be thrown.
```
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present modally an active controller <UIViewController: 0x7fc33e422f50>.'
```
Changelog: Fix crash caused by presenting view controller twice from RCTRedBox
Reviewed By: PeteTheHeat
Differential Revision: D20946645
fbshipit-source-id: 763066e37db4e56efb0118b2e7867ad0724bae81
Samuel Susla
46c77dc296