ENSEMBL-1904: Variation z-menu has a link to population genetics, even when population genetics is greyed out on the variation page.
ENSEMBL-1904: Variation z-menu has a link to population genetics, even when population genetics is greyed out on the variation page.

Added a clause to check if there is any population entries available for variation object.
If number of entries freqs > 0, show the link. Otherwise, not.

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