check  if graphicsDevice._d3dDevice.NativePointer == null

fix for issue #3206.
When WP8 resume an WindowsPhoneGameWindow.Page_OrientationChanged event
might occur too early before the device gets updated. I that case
graphicsDevice._d3dDevice.NativePointer is null and
graphicsDevice._d3dDevice.FeatureLevel fails.

I moved outside the try/catch block to make the code readable and to
handle all possible sources of exceptions.
whitespaces-v
Revert "whitespaces-v"

This reverts commit 22b79cc519a892479559b50061d5735fb3ca76c7.
Merge pull request #3245 from nkast/tncGetHighestSupportedGraphicsProfile

check  if graphicsDevice._d3dDevice.NativePointer == null