Better handling of $label.and.title.separator generation for TOC entry labels: do not generate the separator if label is empty.
Better handling of $label.and.title.separator generation for TOC entry labels: do not generate the separator if label is empty.

oreillymedia/HTMLBook,oreillymedia/HTMLBook,macmillanpublishers/HTMLBook,oreillymedia/HTMLBook,wastemobile/HTMLBook,mushroomgithub/HTMLBook,gitenberg-dev/HTMLBook,gitenberg-dev/HTMLBook,macmillanpublishers/HTMLBook,wastemobile/HTMLBook,mushroomgithub/HTMLBook,mushroomgithub/HTMLBook,macmillanpublishers/HTMLBook,gitenberg-dev/HTMLBook