Error when trying to process removed issue

[jonasraoni]

If an issue is removed from the journal before being uploaded to the staging server, it remains in the deposit list of the plugin, even though, it's never going to be finished.

• Given that it's not possible to remove an issue from the Preservation Network, I think it might make sense to keep removed issues in the list of deposits of the plugin.
• For this specific case, I think it makes sense to remove the item, or at least setup a more helpful error message, to let the user know what has blocked the deposit.