When search results are non-empty, the first item should be highlighted by default indicating that it will be selected when Enter is pressed.

Originally posted by @WunderBart in #19458 (comment)

Description

When initial suggestions are present (see referenced PR) then the input has no value. However when you hit enter the first search suggestion is populated as the link. This shouldn't happen. The suggestion should only become "selected" if the user clicks it or uses the keyboard arrows to select it.

The behaviour should be that hitting enter should show some kind of error indicating no value has been selected/entered and therefore no link can be created.