[RM-6341] deal with the linemeas case (one z, or no extrema found) after pdfrefactor

Created on 2021-02-23 16:03:29 by Didier Vibert. % Done: 0

since #5815 linemeas is broken (it was even before...)

TODO

• skip the pdf candidate search, if only one z scalar instead of a vector
• accept the noextrema found in the case of a z range, and then keep the initial z solution.
• adapt the extremaresults in the resultStore for these cases.