twitter/bootstrap — pull request #3570 by andrewhubbs (2012-05-22 20:58:34+00:00)
Title: Tooltip placement is wrong when the element is SVG in IE 9

IE 9 will return a null for `offsetWidth` and `offsetHeight` when the element is an SVG element.

The result is a NaN error when trying to do arithmetic with a null value when calculating the left/top values for the tooltip placement.

This fix is not perfect because it can result in an off center positioning, but it corrects the error where the top/left CSS will be set to 0 due to a NaN error in the math.