Internal helper for calc_selectivity(). A length-based selectivity
function converts the lengths in gear_params() to weights with the
species' a and b. When those were filled in by mizer rather than
supplied, the selectivity curve sits at weights mizer invented, and the
fishing mortality is wrong in a way nothing else reveals. So it is reported
where the conversion happens and not only where the default is filled in.
signal_defaulted_length_weight(params, species)NULL, invisibly. Called for the report it raises.
A MizerParams object.
The species whose selectivity is set from their length.