drag-action: Fix a compiler warning
drag-action: Fix a compiler warning

Use arguments of the right signedness when passing pointers.

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