Patch for 84134 - 'add pattern' crash

[Damon Chaplin <damon ximian com>]

I've added a patch to:

   http://bugzilla.gnome.org/show_bug.cgi?id=84134

It was crashing if you clicked several times on the 'OK' button of the
'Add Pattern' dialog.

The patch hides the dialog when the button is clicked and sets the flag
to indicate we've acted on it, so it doesn't try to destroy it again if
the user clicks 'OK' twice.

Damon