Fix bug #10263 with assertion violation using telugu-itrans input method.

 src/xdisp.c (RECORD_MAX_MIN_POS): Use IT->cmp_it.charpos only if
 IT->string is nil.

src/ChangeLog

+2011-12-10  Eli Zaretskii  <eliz@gnu.org>
+
+	* xdisp.c (RECORD_MAX_MIN_POS): Use IT->cmp_it.charpos only if
+	IT->string is nil.  (Bug#10263)
+
 2011-12-10  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* nsterm.h (x_free_frame_resources): Declare.

src/xdisp.c

@@ -18887,7 +18887,8 @@ display_line (struct it *it)
 #define RECORD_MAX_MIN_POS(IT)					\
   do								\
     {								\
-      int composition_p = (IT)->what == IT_COMPOSITION;		\
+      int composition_p = !STRINGP ((IT)->string)		\
+	&& ((IT)->what == IT_COMPOSITION);			\
       EMACS_INT current_pos =					\
 	composition_p ? (IT)->cmp_it.charpos			\
 		      : IT_CHARPOS (*(IT));			\