A modal's primary action (blue button in the default theme) can now be invoked
by hitting Enter on the keyboard. This applies to all modals that aren't strict
forms as long as the focus is not on a textarea element.
This happened because the modal controller was not clearing the `name`
attribute, which is used for looking up the controller to call `onClose`
on.
Every page navigation would call the method over and over, breaking
state in odd ways.
