Possible problem with closure test fits

As requested by @wilsonmr in #577 (closed) , I run the 191007-ern-001-31glob fit. Unfortunately, towards the end of the fit I obtain the error message. I'm using the latest version of the code on master.

**** Producing T0 Predictions with Set MMHT2014nnlo68cl

Final Positivity Test Passed all points for POSF2U Passed all points for POSF2DW Passed all points for POSF2S Passed all points for POSFLL Passed all points for POSDYU Passed all points for POSDYD Passed all points for POSDYS

Writing fitinfo file... Computing arclengths... Writing sumrules file... Writing preproc file... Writing params file... Printing grid to file: trial/nnfit/replica_1/trial.exportgrid Initialising evolution with 196 x-points terminate called after throwing an instance of 'std::out_of_range' what(): map::at Aborted (core dumped)