Validate RedDrawable before allocating drawable
Validate RedDrawable before allocating drawable

Avoid unnecessary allocation (and possibly leaking) if the RedDrawable
is not valid.

Related to: rhbz#1135372

fgouget/spice,ya-mouse/spice,freedesktop-unofficial-mirror/spice__spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,ya-mouse/spice,SPICE/spice,Fantu/spice,Fantu/spice,SPICE/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,fgouget/spice,ya-mouse/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice