Do not check GList/GSList references against NULL
Do not check GList/GSList references against NULL

NULL is a valid empty GList/GSList. Based on patch by Yu Feng,
fixes bug 578198.

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