codegen: Use set_delegate_target for null literals
codegen: Use set_delegate_target for null literals

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