Enter should submit the form, not open the next dropdown

Problem/Motivation

Pressing enter on a focused form element opens the next dropdown rather that submitting the form.

Steps to reproduce

1. Enable multiselect_dropdown_bef_test.
2. Add a title field to the view filters as the first item.
3. View the test view.
4. Enter some text in the text filter.
5. Press enter.

The next dropdown is opened, rather than submitting the view.