#373 Post-Python 3: Edit Series submissions can be created and filed for deleted series

[Ahasuerus]

Edit Series submissions can be created and filed for deleted series. The problem is two-fold.

First, if the edit form for a series is displayed in a browser window, the editor can create a submission even if the series record was deleted between the time the edit form was loaded by the browser and the time the "Submit" button was clicked.

Second, although the submission review logic prevents the reviewing moderator from approving an Edit Series submission for a deleted series, if the submission record is already pre-loaded in the submission review window when the series record is deleted, clicking "Approve" will proceed with updating the no longer existing Series record. It can create bogus entries in the "webpages" table and a bogus Notes record pointing to a non-existing series record.