Change return type to Option<u32>
Change return type to Option<u32>

gkoz/gtk-rs-gtk,drewet/gtk,Susurrus/gtk,insanebits/gtk,Susurrus/gtk,rust-gnome/gtk,EPashkin/rust-gnome-gtk,gkoz/rust-gnome-gtk,LordSentox/gtk,gkoz/rust-gnome-gtk,EPashkin/rust-gnome-gtk,gkoz/gtk-rs-gtk,insanebits/gtk,drewet/gtk,daa84/gtk,rust-gnome/gtk,LordSentox/gtk,daa84/gtk