Search error when the field contains spaces

Hi.

I've noticed that if you search writing a text with spaces it doesn't find anything. I've looked the code and found that:

function profilesearch_search_form_submit($form_id, $form_values) {

$searchstring = str_replace(" ", "+", $form_values['search']);

return 'profilesearch/'. $searchstring;
}

If you use "$searchstring = str_replace(" ", " ", $form_values['search']);" instead, it works fine. It's like doing nothing. Is there a reason why it is used the replacing?

Bye! And thanks in advance!