[Android] Don't flip GLES if window was destroyed

[peak3d]

Description

If window is destroyed (no surface to render GL available) we should avoid to render on it to avoid abort exceptions. This is what this PR is doing.

Motivation and Context

Remove more ANR's / crashes

How Has This Been Tested?

• Enable kill background tasks in android phone settings.
• Launch kodi
• Switch of screen from mobile.

Without PR you'll find a fatal abort in kodi.log

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)