After playing around with this, I may press the down arrow key to select the single item listed then press the enter key. It would be quicker to have the single item in the list already highlighted and selected. This would allow me to simply press enter to have the item added. This would be quicker than a down arrow key press first.
If I am pressing CTRL+SPACE, I am intentionally opening this pop-up. Is there a good reason not to highlight the first item for me automatically?