Cache the db when looking up feature_cvterms and prevent blowing up if dbxref is undef
Cache the db when looking up feature_cvterms and prevent blowing up if dbxref is undef

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