Created by: Xegyn
when used with a sticky footer layout.
Fixes issue that was introduced in Bootstrap 3.3.0 (reference: https://github.com/twbs/bootstrap/issues/15032), introduced by this commit: https://github.com/twbs/bootstrap/commit/724c4f526cd56a28bb305fe6f1f31f3091bf2cd6
The scrollable height used to be the document, which would be correct in the case of using a sticky footer layout where body is set to 100%, which is essentially the viewport height.
The commit that changed it to body height broke this, but fixed a bug where the document height was smaller than the body height.
This fix takes the max of the document height and body height, which should allow the affixed element to have the correct position in either case.