There is no easy way around this. I would suggest you leave it as it is since most won’t click on the page when a dropdown is presented on hover. I would suggest you link to the main page among the dropdown items just in case the user wants to skip the dropdown menu pages to avoid more details.
We could have removed the restriction that a menu should have a link associated with it – but for a long time now WordPress has been forcing a link to be present when adding a menu item and you could erase it only by editing the menu item after addition(more of a after thought).