Add protection against null TrackParameters pointer (ATLASRECTS-8115)
Follow up to !74306 (merged)
Old code implicitly included a nullptr check
std::unique_ptr<const Trk::TrackParameters> parm( m_extrapolator->extrapolateDirectly(ctx, *input, perigeeSurface) );
const Trk::Perigee*extrapolatedPerigee = dynamic_cast<const Trk::Perigee*> (parm.get());
if (!extrapolatedPerigee) {
Restored here to fix ATLASRECTS-8115
FYI @christos