The Dummy Cards that are created when the database is being set up are not essential once all the stacks (levels) have real data cards in them. To remove a Dummy Card, go to the Dummy Card, go into "Debug" mode, and select "Delete Card" from the Edit pull-down menu. This is the one time that you get to violate that "Warning!" message that you must have read by now.
You should not remove a Dummy Card if you expect the number of real cards on its level to drop back to zero. This condition will cause deletion failures. You will get the message that tells you that you can't remove the last card from a stack.
If you're sure that a level will keep some population of real cards, go ahead and remove the Dummy Card if it is annoying you.