Dropdown menu errors out when navigating with keyboard

[cheng-tan]

Steps

1. Use the dropdown with Dropdown.Menu and Dropdown.Item. For example: http://react.semantic-ui.com/modules/dropdown#search-in-menu

2. Click on the Search In-Menu dropdown to open it.

3. Press down arrow on the keyboard, then it errors out.
   The error message in the console is: app.61ca82f….js:6621 Uncaught TypeError: Cannot read property 'length' of undefined

Expected Result

User should be able to navigate through the dropdown using up and down arrow.

Actual Result

It throws errors if the dropdown is created with Dropdown.Menu and Dropdown.Item

Version

0.61.7

[levithomason]

Per the info message on the example:

The example below shows the desired markup but is not functional. Needs to be defined via shorthand, which is not yet possible.
If there's no pull request open for this, you should contribute!

This is not a bug but a missing feature, PRs welcome.

[levithomason]

Closing as a dupe of #889