has_class modified to not create 'class' key if given class is not found; return undef when false instead of 0
has_class modified to not create 'class' key if given class is not found; return undef when false instead of 0

Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode