diff -upr mate-control-center/font-viewer/font-thumbnailer.c mate-control-center-test/font-viewer/font-thumbnailer.c
--- mate-control-center/font-viewer/font-thumbnailer.c	2015-08-30 17:05:43.163571736 +0200
+++ mate-control-center-test/font-viewer/font-thumbnailer.c	2015-08-30 17:01:43.533056000 +0200
@@ -181,7 +181,7 @@ main (int argc,
     cairo_t *cr;
     cairo_text_extents_t text_extents;
     cairo_font_face_t *font;
-    gchar *str;
+    gchar *str = NULL;
     gdouble scale, scale_x, scale_y;
 
     const GOptionEntry options[] = {