Bug: _ensureHighlightVisible throws [ui.select:choices] Expected multiple .ui-select-choices-row but got '0'.

[zollinger]

Bug description:

As _ensureHighlighVisible() is being called in a setTimeout() might be triggered in situations where the ui-select is actually closed and thus, the options aren't rendered. This clashes with the assertion of "choices.length > 1" made in _ensureHighlightVisible. It happens frequently on slower machines when double clicking the input field.

This is the same bug that was observed in #1355 (which was not a duplicate of #224, as the error thrown is quite different).

Link to minimally-working plunker that reproduces the issue:

To reproduce:

1. Open plunkr below
2. Enable Chrome performance throttling and set it to 10 - 20x slower
3. Double click the ui-select element

http://plnkr.co/edit/ShmVlq3Xk7QVHurt6BLU?p=preview

Version of Angular, UI-Select, and Bootstrap/Select2/Selectize CSS

Angular: latest

UI-Select: latest

Bootstrap/Select2/Selectize CSS (if applicable): Bootstrap