[RM-6123] set FittedTplMeiksinIdx output value to -1 when non applicable

Created on 2020-11-13 14:38:44 by Didier Vibert. % Done: 100

FittedTplMeiksinIdx is an output given for each redshift solution and refers to the igm extinction curve selected for the model. The curves comes from Meiksin 2005, 7 curves times 11 redshift bins .The index goes from 0 to 6, selecting one of the 7 curves of the redshift bin corresponding to the redshift solution.

when the IGM extinction is not applied or when the the redshift is too small, there is no extinction applied. In such a case the output is currently left to zero.

A non-ambiguous value of "-1" should be set instead