Footer on small viewports
The footer doesn't display well on small viewports. A bigger ones, the footer needs to be attached at the bottom of the window. This imply to fix the footer height to keep it working (this is described by bootstrap in their documentation).
On smaller viewports, as shown on the image, the fixed size of the footer creates an issue. The sticky footer technique isn't relevant in this case as there will always be enough data to keep the footer at the bottom of the screen. Therefore, a media query would be enough to remove the position: absolute
and keep a normal behaviour.