Whole site searched with no data input

"Enable filtering by content type" checkbox ticked.
"Content type" checkbox ticked.

If I then choose to do a search either with advanced or normal (trip search), and I do not enter any text in the search box, and only select a certain content type, I get a hit for the whole site for that particular content type.

I was hoping for an error message to be returned, and ask the user to at least input some characters, like it does in the normal Drupal search.

Hope this makes sense.

Thanks
Stephen