combo-box: don't use NULL when setting the ClutterText "text" property
combo-box: don't use NULL when setting the ClutterText "text" property

clutter-project/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx