Using index in help can crash info

[Vitezslav Crhonek]

Hi,

when indexing help page in info (after another index on another page was 
already built), segmentation fault occurs. Steps to reproduce:

a) $ info info
b) hit "i" and then hit "RETURN" (you'll see index window)
c) hit "h" (you'll see help window)
d) hit "i" (you'll see Segmentation fault)

The problem is in do_info_index_search function within indices.c, where 
the NULL pointer is accessed.

Patch bellow fixes the issue.


--- indices.c.orig      2010-08-30 16:39:25.200624620 +0200
+++ indices.c   2010-08-30 16:42:01.683624488 +0200
@@ -192,6 +192,7 @@
      index for, build and remember an index now. */
   fb = file_buffer_of_window (window);
   if (!initial_index_filename ||
+      !fb ||
       (FILENAME_CMP (initial_index_filename, fb->filename) != 0))
     {
       info_free_references (index_index);