twitter/bootstrap — pull request #3035 by BigBlueHat (2012-04-12 13:40:49+00:00)
Title: made .popover-title hidden if empty via CSS

I'd attempted this earlier with some rather complex JS (#1975). This version uses only CSS, and uses text-indent and line-height (vs. padding), so the title takes up no space if it's empty.

Hope it's helpful.