Prevent dereferencing of nullptr
A segfault of a Moore test in optimized builds in lhcb-gaudi-head is caused by a nullptr that is dereferenced.
This prevent it to happen (although I'm not sure what to expect there).
The potential nullptr dereferencing has been there for a while, but it got exposed only recently by some changes in Gaudi and LHCb!4289 (merged) removes an undefined behavior always exposing the problem.