CategoryWalker, if cat_name is empty, do not append the empty a tag to the output

[samo9789]

If the theme is customized to skip some categories by doing something like add_filter('list_cats', 'hideSomeCatgory') and returning a null or an empty string as cat name, the CategoryWalker will append an empty html element to the output

Hi,

This is my first contribution to an existing open source project. I hope I respected the ticket creation and patch submission process and that this can help improve Wordpress. I hope someone will review this correction.

Take care,
samo9789

patch for described minor bug