Get parentNode only for div.track_name
Get parentNode only for div.track_name

Fixing a bug introduced in 3c513d3 that breaks 'Enable/Disable all' functionality.
parentNode (i.e. li.track) should only be considered if clicked on a div.track_name.

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