CGUIControlSettings: add missing breaks in switch-statement
overlays: Only render GUI subs in fullscreen

This should fix the issues after d567178fdedefff5ea6366da05f9175aea814bac

The code must be fixed to disable all GUI scaling for the rendering
to work in windowed mode too. This reverts back to old behavior of
not rendering text subtitles in windowed mode.
settings: check setting type before casting to CSettingList