avoid spurious implicit copy of MCVertex
Due to mistake in MCVertex, it is possible to assign a LHCb::MCVertex const*
to a LHCb::MCVertex const&
by making an implicit(!) temporary MCVertex
. This MR avoids the copy.
Note: LHCb!4843 will remove this implicit conversion, and hence this MR must either be merged prior to, or together with, LHCb!4843
Edited by Gerhard Raven