girwriter: Fix crash in attribute handling
girwriter: Fix crash in attribute handling

Fixes bug 629364.

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