Fix crash when selecting a shiva filter or generator

[Cyrille Berger]

On Tuesday 10 November 2009, Boudewijn Rempt wrote:
> On Tuesday 10 November 2009, Cyrille Berger wrote:
> > hi,
> >
> > Those two patches fixes crashes when selecting some of the shiva filters
> >  that have already been used, and also when reconfiguring some of the
> >  generators.
> >
> > I would like to backport them to branch/2.1.
> 
> I trust your expertise here, so it's okay as far as I'm concerned.
well, while it is nice to have such confidence, the review is intented to be 
sure the "expert" has not overlook something ;p

-- 
Cyrille Berger