don't add opt_empty_tracks if the opt_empty_tracks parameter is set to 0. alter type of track for canvas if track is displayed on both strands
don't add opt_empty_tracks if the opt_empty_tracks parameter is set to 0. alter type of track for canvas if track is displayed on both strands

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