iconhelper: Move invalidation check
iconhelper: Move invalidation check

Just do the invalidation check once, there's no need to do it in every
branch of the switch.

Also remove useless checks: These functions will not be called if we
already have a rendered surface.

grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita