Fix for issues #1782 & #1767

[psegalen]

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  Short description of what this resolves:

Issue #1767 is about modal flickering, it is caused by assigning decimal dimensions on modals, the fix just adds a Math.round() to width and height for Frames.

Issue #1782 is about a crash happening only on iOS when UI Kitten tries to measure a node that RN did not find, Android seems to support it but it makes an iOS app crash.

[psegalen]

I think it fixes #1751 so it may be taken for a duplicate of #1752 but it fixes 2 issues in one PR

[robpearmain]

Hi. Is there a release, or planned release soon to fix the measureInWindow issue please

https://github.com/facebook/react-native/issues/41730

[rklomp]

@psegalen See my comment at https://github.com/akveo/react-native-ui-kitten/issues/1767 and https://github.com/akveo/react-native-ui-kitten/issues/1802

I had to use Math.floor() to fix my issue instead of Math.round().