Portfolio Items on Single Page Layout

I’ve created a Portfolio page using Portfolio Items that all have empty (blank) entries for Custom URL. This is simply to show a series of photos on 1 page. However, when I click on the photos, every one takes me to a blank page (on the same tab). I thought if I left the Custom URL field blank, clicking on a Portfolio Item would not result in following a link. Is this incorrect? How to I just show Portfolio Items without any URLs behind them? Thanks.