Deleted app stuck in Launchpad

I have recently tried to update an app from the App Store, but it just stuck on "Waiting..." and wouldn't update. So what I did is I deleted the app from the Applications folder and also emptied the Trash, but now the app icon is grey and still stuck in Launchpad, also still saying "Waiting...".

How can I get rid of that icon from the Launchpad now? I've tried clicking and holding until the "x" appears, but after it asks "Are you sure you want to delete" and I click "Delete" it's still there.