Property 'window' missing on game list

[wackerl91]

• Luna Version: 0.7.0-rc7
• nVidia GeForce Experience Version: N/A
• Moonlight Embedded Version: N/A
• OSMC Version: 2017.02-2

Expected Behaviour:
Entering / leaving the game list should always be possible without an exception being thrown (even when rendering is not complete).
If it the view can't be loaded log it as an error and show a dialog to the user.
Cleanup of window objects should happen when shutting down Luna (i.e. pretty much the same how settings view is currently handled) for all views.

Actual Behaviour:
Exception is thrown during rendering of the game list, circumstances unknown.