nnnick/Chart.js — pull request #641 by lauzierj (2014-09-20 11:49:55+00:00)
Title: Does not display tooltips when the output of the template is blank.

Originally, I made an option (showEmptyTooltips) and worked that in, but who would ever want to see empty tooltips?

A use case for this would be using a doughnut chart with a transparent section to display an incomplete circle.