input-device: Do not pick() on NULL stages
input-device: Do not pick() on NULL stages

If the stage associated to the InputDevice is not set we should
short-circuit out and return NULL. This will result in a pick()
done on the event's stage - if applicable.

http://bugzilla.moblin.org/show_bug.cgi?id=9602

jigpu/clutter,collects/clutter,djdeath/clutter,kerrickstaley/clutter-vala,dlespiau/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,GNOME/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,Distrotech/clutter,heysion/clutter-clone,djdeath/clutter,djdeath/clutter,Distrotech/clutter,GNOME/clutter,ebassi/clutter,heysion/clutter-clone,spatulasnout/clutter,spatulasnout/clutter,nobled/clutter,collects/clutter,ebassi/clutter,djdeath/clutter-android,djdeath/clutter-android,collects/clutter,jigpu/clutter,Distrotech/clutter,dlespiau/clutter,djdeath/clutter-multithreaded,djdeath/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,kerrickstaley/clutter-vala,spatulasnout/clutter,ebassi/clutter,Distrotech/clutter,heysion/clutter-clone,collects/clutter,Distrotech/clutter,ebassi/clutter,djdeath/clutter,collects/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,jigpu/clutter,jigpu/clutter,heysion/clutter-clone,heysion/clutter-clone,djdeath/clutter,jigpu/clutter,spatulasnout/clutter,spatulasnout/clutter,djdeath/clutter-multithreaded,dlespiau/clutter,djdeath/clutter-android,nobled/clutter,nobled/clutter,kerrickstaley/clutter-vala,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,djdeath/clutter-android,kerrickstaley/clutter-vala,GNOME/clutter,GNOME/clutter