Sampler not at end of Sbend in visualiser

[William Shields]

In the visualiser at least, the sampler for an sbend that is split into several segment appears at the end of the first segment, not the whole element (see attached screenshot).

[Laurie Nevay]

Fixed. There was an error in the sampler attachment logic in BDSBeamline.cc given the recent move to samplers at the end of items.