Fix: Fixed NullReferenceException in MainPageViewModel.UpdateInstancePropertiesAsync

[hishitetsu]

I don't know why an exception is thrown, but since this process only updates the window title, I ignore the exception when it is thrown.

Resolved / Related Issues

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  https://appcenter.ms/orgs/FilesApp/apps/Files/crashes/errors/2912768630u/overview

Validation
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[yaira2]

LGTM