dova: Fix code generated for instance casts
dova: Fix code generated for instance casts

spidermonkdust/vala,GNOME/vala,severinh/vala,jessevdk/vala,tjol/vala-tjol,rvu95/vala,rvu95/vala,frida/vala,spidermonkdust/vala,Distrotech/vala,playya/vala,GNOME/vala,kamanashisroy/aroop,frida/vala,flobrosch/vala-fixes,frida/vala,kamanashisroy/aroop,tjol/vala-tjol,playya/vala,frida/vala,GNOME/vala,severinh/vala,Distrotech/vala,flobrosch/vala-fixes,jessevdk/vala,kamanashisroy/aroop,playya/vala,rvu95/vala,severinh/vala,Distrotech/vala,xdave/pvala,jessevdk/vala,flobrosch/vala-fixes,GNOME/vala,tjol/vala-tjol,frida/vala,spidermonkdust/vala