add space when searching for theme

[chrisdias]

Press F1, Change Color Theme.
Choose Install Additional Color Themes from the quick pick.

The extension viewlet opens with category:themes pre-populated in the search box and the caret is at the end of the line, after the s:

If I start typing now (e.g. start looking for a theme) I don't get any results because I need a space between category:themes and whatever I'm searching for, in this case cobalt:

It would be nice to add the space automatically so that I can just start typing, not having to remember to press space first.