vapigen: Fix crash in parse_signal
vapigen: Fix crash in parse_signal

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