Fixed missing member initializations in functors leading to segmentation fault

This was found in Lifetime_t and ComputeDecayLengthSignificance_t. In both cases the member m_lifetime_calc is never initialized (no inline initialization and no constructor) and is an object holding a pointer, suppositely null initially. We must have been lucky so far that there was a zero in memory at that place, but I was not more lucky when testing the new I/O for output.