Make menu link expand instead of redirect

Question

Let's say that I have a following menu:

• A
  • A1
  • A2
• B

Which looks like this:

When somebody clicks on the arrow on the right of A (or in the empty space on the left of the arrow) the submenu expands, but when they click on A it redirects to the page set in admin/structure/menu/item/785/edit.

I want A to also expand the submenu instead of redirecting. How do I achieve that in Drupal 7?