hgview #7932 find_next triggers a trace [validation pending]

see :

Traceback (most recent call last):
 File "/home/auc/rep/public/hgview/hgview/gtk/hgview_gtk.py", line 49, in watched
   ret = meth(self, *args, **kw)
 File "/home/auc/rep/public/hgview/hgview/gtk/hgview_gtk.py", line 766, in on_button_find_clicked
   res = self.find_next_row( it )
 File "/home/auc/rep/public/hgview/hgview/gtk/hgview_gtk.py", line 708, in find_next_row
   rexp = re.compile( txt )
 File "/usr/lib/python2.5/re.py", line 188, in compile
   return _compile(pattern, flags)
 File "/usr/lib/python2.5/re.py", line 241, in _compile
   raise error, v # invalid expression
sre_constants.error: unbalanced parenthesis