Check if child view != null before dropping

[chrusart]

Fixes our top crash when framework try drop a view from parent, but it's a null (already removed etc.).

Fixes #20288

Test Plan:

No test plan, crashes happen rarely and very hard to reproduce.

Release Notes:

[ANDROID] [BUGFIX] [NativeViewHierarchyManager.java] - Fixes crash when trying to drop null child view

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[chrusart]

CLA signed

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[xkrsz]

This may resolve the crashes, but I think there's an underlying issue in Android 8.0 resulting in potentially broken UI.

[chrusart]

You think it's an underlying issue in Android 8.0 because it happen only on this version? There is also a possibility that in 8 were some changes and RN didn't make adjustments for it.
But this check will not harm, right? Maybe in some future versions something else will break that this child will be null again. I'm not a fan of hiding/patching things, but to find the source of a problem as well. This check will resolve crashes, but will not make harder to find the real reason as it should make crashes or errors in more obvious place, this crash is probably just a side effect of a real problem.

[xkrsz]

You’re right, that’s a more probable scenario.

I would suggest logging a warning if child == null, this should improve visibility of the root cause.

[chrusart]

Log added.

[facebook-github-bot]

@chrusart I tried to find reviewers for this pull request and wanted to ping them to take another look. However, based on the blame information for the files in this pull request I couldn't find any reviewers. This sometimes happens when the files in the pull request are new or don't exist on master anymore. Is this pull request still relevant? If yes could you please rebase? In case you know who has context on this code feel free to mention them in a comment (one person is fine). Thanks for reading and hope you will continue contributing to the project.

[chrusart]

@mkonicek hi, just mention you to get reviewer for this PR as bot says :)
Can you review code? Not sure you work still for RN.

[chrusart]

@hramos hi, is @mkonicek still working for facebook, who can do review now?

[chrusart]

@hramos ?

[facebook-github-bot]

hramos is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[react-native-bot]

@chrusart merged commit af181fb into facebook:master.

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