Fix scaling of inherited images within a group or another widget
Enhance videodescrip statetype to recognize more resolutions

Fixes #10095

Signed-off-by: Stuart Morgan <smorgan@mythtv.org>
Set previewgenerator point to NULL after deletion. If by chance the same generator has ended up in the queue twice this may possibly cause a segfault when tearing down the preview generator. Refs #10564