Scrolling horizontally in grid with pinned columns causes the grid to scroll to the top of the viewport (Safari)

Browser: Safari 10.0.2 UI-Grid: v3.1.1

Steps to Reproduce

1. Scroll down vertically so that the top row of the grid is out of the viewport.
2. Scroll horizontally to either edge within the main (body) viewport
3. Continue to try to scroll horizontally past the edge of the viewport.
4. The grid (pinned and body viewports) will be instantly scrolled vertically to the top of the viewport

This is reproducible in Safari on the Pinning Tutorial page of the ui-grid website.