Fix the step issue of lit frame pattern ranges

This fix the range step issue. The step was set to zero in the case of single train in the range. This raises an exception when the range is expanded to fill the gaps in LitFrameFinder data:

See log

~/proj/pycalibration/.venv/lib/python3.8/site-packages/extra_redu/litfrm/selection.py in _make_selection(self, guess_missed, crange, energy_threshold)

    151 # make train list
    152 jN = j0 + ntrn + missed
--> 153 tid_nrm[j0:jN] = np.arange(
    154     t0, tN + one, step, dtype=self.tid_type)
    155 ptrn_ix[j0:jN] = ptrn_id

ValueError: Maximum allowed size exceeded

See ticket #147818