Fix initialization of nullable structs
Fix initialization of nullable structs

Fixes bug 579758.

rvu95/vala,jessevdk/vala,frida/vala,GNOME/vala,themiwi/vala,Distrotech/vala,flobrosch/vala-fixes,spidermonkdust/vala,severinh/vala,phako/vala,frida/vala,jessevdk/vala,tjol/vala-tjol,frida/vala,xdave/pvala,playya/vala,playya/vala,kamanashisroy/aroop,kamanashisroy/aroop,themiwi/vala,GNOME/vala,tjol/vala-tjol,Distrotech/vala,frida/vala,rvu95/vala,spidermonkdust/vala,lovebug356/vala,spidermonkdust/vala,lovebug356/vala,flobrosch/vala-fixes,kamanashisroy/aroop,playya/vala,frida/vala,Distrotech/vala,Jc2k/vala,jessevdk/vala,severinh/vala,tjol/vala-tjol,flobrosch/vala-fixes,GNOME/vala,severinh/vala,themiwi/vala,Jc2k/vala,GNOME/vala,rvu95/vala,phako/vala