Check for pop_id in qtl.pl and throw an error if not given
Check for pop_id in qtl.pl and throw an error if not given

Function calls with leading & were also removed. Let's not do that.

solgenomics/sgn,solgenomics/sgn,solgenomics/sgn,solgenomics/sgn,solgenomics/sgn,solgenomics/sgn,solgenomics/sgn