Replace deprecated KeyWindow property for iOS15

[ghost]

:sparkles: What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Fix intermittent NRE crash for iOS15.1 by having an alternative way to get the window object.

:arrow_heading_down: What is the current behavior?

When restarting an app using iOS15.1 the pop-up crashes and doesn't show up.

:new: What is the new behavior (if this is a feature change)?

The pop-up works as expected on iOS 15.1.

:boom: Does this PR introduce a breaking change?

No

:bug: Recommendations for testing

Restart the app a few times while opening a pop-up using the plugin.

:memo: Links to relevant issues/docs

Applied fix from this source: https://developer.apple.com/forums/thread/695932

:thinking: Checklist before submitting

• [ ] All projects build
• [x] Follows style guide lines
• [ ] Relevant documentation was updated
• [x] Rebased onto current develop

[ghost]

@LuckyDucko can you review this PR when you have time, please? Let me know if you need more info regarding this PR. Thanks!

[xleon]

Hi guys, can we please merge this PR? The requested changes have been done already by @arctouch-andresato

[LuckyDucko]

@xleon My Apologies, usually i leave @martijn00 for merging, as he is in control of updating the NuGet. However, as i have reviewed this, i'm able to merge, just not able to make a NuGet

[ghost]

Hi @rotorgames, @martijn00, do you know when we'll have a new Nuget release with this change?

[ramonB1996]

Yes please, this bug causes problems for the MaterialMenuButton on iOS 15+ as well, so would be nice if the nuget package is coming soon! :)

[rjantz2]

@martijn00 Could we get an updated nuget package soon, please?

[xleon]

This fix is actually working. Thanks for the help.