LT-14861 Fix null refs in WinKeyboardAdapter.GetLayoutNameEx

The issue reports a null reference which I can't reproduce
in this method. I've handled all the cases that look like
possible null refs.

Change-Id: I4cd0cddfc8cbd7efc5edb6cecd81237e46eba987
Merge "LT-14861 Fix null refs in WinKeyboardAdapter.GetLayoutNameEx" into fw/KeyboardingV2