Avoid a crash in mouse-highlight of Speedbar frames.

 src/xfaces.c (face_at_buffer_position): Avoid repeated evaluation of
 face ID by FACE_FROM_ID, and avoid a crash when mouse is moved
 from an Org mode buffer to a Speedbar frame.

src/ChangeLog

 2011-08-19  Eli Zaretskii  <eliz@gnu.org>
 
+	* xfaces.c (face_at_buffer_position): Avoid repeated evaluation of
+	face ID by FACE_FROM_ID, and avoid a crash when mouse is moved
+	from an Org mode buffer to a Speedbar frame.
+
 	* xdisp.c (RECORD_MAX_MIN_POS): If the display element comes from
 	a composition, take its buffer position from IT->cmp_it.charpos.
 	Fixes cursor positioning at the beginning of a line that begins

src/xfaces.c

@@ -6008,9 +6008,18 @@ face_at_buffer_position (struct window *w, EMACS_INT pos,
 
   *endptr = endpos;
 
-  default_face = FACE_FROM_ID (f, base_face_id >= 0 ? base_face_id
-			       : NILP (Vface_remapping_alist) ? DEFAULT_FACE_ID
-			       : lookup_basic_face (f, DEFAULT_FACE_ID));
+  {
+    int face_id;
+
+    if (base_face_id >= 0)
+      face_id = base_face_id;
+    else if (NILP (Vface_remapping_alist))
+      face_id = DEFAULT_FACE_ID;
+    else
+      face_id = lookup_basic_face (f, DEFAULT_FACE_ID);
+
+    default_face = FACE_FROM_ID (f, face_id);
+  }
 
   /* Optimize common cases where we can use the default face.  */
   if (noverlays == 0