text_property_stickiness

[Chong Yidong]

Regarding the following FOR-RELEASE item:

  ** text_property_stickiness can be called with a POS value that is
     before BEGV.

  text_property_stickiness is called from get_pos_property, which is
  called from find_field, which is called from various user-level
  functions in editfns.c.

This little change to text_property_stickiness should be all that's
needed to fix it, no?

*** emacs/src/textprop.c.~1.147.~       2006-05-17 13:33:46.000000000 -0400
--- emacs/src/textprop.c        2006-06-24 16:24:46.000000000 -0400
***************
*** 1787,1792 ****
--- 1787,1794 ----
        /* PROP is rear-non-sticky.  */
        is_rear_sticky = 0;
      }
+   else
+     return 0;
  
    /* Consider following character.  */
    front_sticky = Fget_text_property (pos, Qfront_sticky, buffer);