Hitting enter redirects to the Sphinx search page

[agjohnson]

It's pretty common to hit enter at the end of the search query and expect the search query to be submitted, but instead the user is redirected to the Sphinx search page. I've noted this UX issue in the past and I've had feedback that this UX is confusing as well.

This is probably more of an issue for the addons implementation, which probably won't repeat this pattern either way. But noting here in case for now.