Fix bug #16819 with dereferencing invalid face pointer.

 src/xdisp.c (init_iterator): Don't dereference a bogus face
 pointer.

src/ChangeLog

+2014-02-20  Eli Zaretskii  <eliz@gnu.org>
+
+	* xdisp.c (init_iterator): Don't dereference a bogus face
+	pointer.  (Bug#16819)
+
 2014-02-20  Glenn Morris  <rgm@gnu.org>
 
 	* data.c (Fdefalias): Doc fix.

src/xdisp.c

@@ -2928,7 +2928,7 @@ init_iterator (struct it *it, struct window *w,
       /* If we have a boxed mode line, make the first character appear
 	 with a left box line.  */
       face = FACE_FROM_ID (it->f, remapped_base_face_id);
-      if (face->box != FACE_NO_BOX)
+      if (face && face->box != FACE_NO_BOX)
 	it->start_of_box_run_p = true;
     }