Fix bug #16509 with segfault in an assertion when exiting due to missing font.

src/w32fns.c (unwind_create_frame): Avoid crashing inside assertion
 when the image cache is not yet allocated.

src/ChangeLog

@@ -1,3 +1,8 @@
+2014-01-21  Eli Zaretskii  <eliz@gnu.org>
+
+	* w32fns.c (unwind_create_frame): Avoid crashing inside assertion
+	when the image cache is not yet allocated.  (Bug#16509)
+
 2014-01-21  Dmitry Antipov  <dmantipov@yandex.ru>
 
 	* buffer.c (Fkill_buffer): When killing an indirect buffer,

src/w32fns.c

@@ -4250,7 +4250,9 @@ unwind_create_frame (Lisp_Object frame)
 #ifdef GLYPH_DEBUG
       /* Check that reference counts are indeed correct.  */
       eassert (dpyinfo->reference_count == dpyinfo_refcount);
-      eassert (dpyinfo->terminal->image_cache->refcount == image_cache_refcount);
+      eassert ((dpyinfo->terminal->image_cache == NULL
+		&& image_cache_refcount == 0)
+	       || dpyinfo->terminal->image_cache->refcount == image_cache_refcount);
 #endif
       return Qt;
     }