Widget hamburger menu does fun things

[samuelsidler]

I'm not really sure how to describe this, but on mobile – iPhone 6S – when I tap the widget hamburger menu, things... get weird. It looks like the widget menu appears is under the header and subnav instead of on top of it. But there's other weird behavior like an extra black bar on the top of the page. The entire thing could use some polishing.

Screenshot attached.

[Ipstenu]

Happens on an iPad Mini as well.

It's the secondary menu (on the right), not the default .org one on the left.

[pento]

In 3634:

Breathe: Make the sidebar play nicer on mobile Safari.

There were some hacks added to Breathe years ago, to fix some mobile Safari bugs - now they're causing problems, so override them.

Fixes #1799.