Single-column board view on iOS has break after "first column"'s end

[mileswwatkins]

Seen in iOS Mobile Safari and iOS Firefox, but no other platforms. There persists a vertical break after the end of what-would-be-the-first-column-of-two when looking at the two-column view.

From Browserstack:

From my phone:

cc #213

[alykat]

Not completely fixed, but hopefully much improved. There are still a couple extra pixels that shouldn't be here, but I'm running out of ideas to fix it that don't also affect other browsers.