text: Do not segfault with NULL :font-name
text: Do not segfault with NULL :font-name

Make sure that we have a fall back in place for the default font name
string, and use g_strcmp0 to protect ourselves from NULL strings.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2417

dlespiau/clutter,collects/clutter,djdeath/clutter-multithreaded,jigpu/clutter,djdeath/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,jigpu/clutter,spatulasnout/clutter,jigpu/clutter,Distrotech/clutter,GNOME/clutter,kerrickstaley/clutter-vala,kerrickstaley/clutter-vala,ebassi/clutter,nobled/clutter,djdeath/clutter-android,djdeath/clutter,dlespiau/clutter,djdeath/clutter-android,djdeath/clutter,GNOME/clutter,heysion/clutter-clone,dlespiau/clutter,heysion/clutter-clone,jigpu/clutter,kerrickstaley/clutter-vala,jigpu/clutter,spatulasnout/clutter,jigpu/clutter,collects/clutter,djdeath/clutter,djdeath/clutter-android,djdeath/clutter-android,Distrotech/clutter,spatulasnout/clutter,spatulasnout/clutter,kerrickstaley/clutter-vala,ebassi/clutter,ebassi/clutter,ebassi/clutter,heysion/clutter-clone,GNOME/clutter,GNOME/clutter,djdeath/clutter,Distrotech/clutter,nobled/clutter,GNOME/clutter,djdeath/clutter-multithreaded,ebassi/clutter,collects/clutter,Distrotech/clutter,djdeath/clutter-android,Distrotech/clutter,djdeath/clutter,djdeath/clutter-multithreaded,heysion/clutter-clone,collects/clutter,nobled/clutter,Distrotech/clutter,spatulasnout/clutter,collects/clutter