Accessibility: aria-controls references an ID that doesn't exist

[adamjohnson]

Steps to reproduce the issue

1. View the demo.
2. Shrink the Priority+ navigation so that "More" is displayed.
3. Right click "More" > Inspect Element.

Results

1. The <button> tag has aria-controls="menu", like so:

<button aria-controls="menu" class="nav__dropdown-toggle priority-nav__dropdown-toggle priority-nav-is-visible" prioritynav-count="1">more</button>

Expected results

The <ul> below the <button> should have id="menu". Currently, it does not.

<ul aria-hidden="true" class="nav__dropdown priority-nav__dropdown">
  ...
</ul>

aria-controls documentation/references:

• aria-controls spec
• Using the aria-controls attribute by Léonie Watson