how do I re-enable additional dialogs?

In my WP back-end, I wanted to delete an image form my library (by going into “Insert media”, selecting the picture and selecting “Delete permanently” under Attachment Details). I was asked in the pop-up window of the “delete permanently” action if I wanted to “prevent this page from creating additional dialogs”, which I said yes to, but now I can’t delete any other images! When I click on “delete permanently”, nothing happens. I guess I need this “additional dialog” to delete my images…So my question is: how do I reverse this, how do I re-enable additional dialogs?

Thank you so much for your help! 🙂