#351 Post-Python 3: Edit Title can create a submission for a non-existent title ID

[Ahasuerus]

Edit Title can create a submission for a non-existent title ID. To recreate the problem, pull up the Edit Title form for an existing title, then delete the title in a different window. When you click "Submit" in the first window, a submission will be created.

This isn't a significant issue because the submission review page will flag the submission as no longer valid and force the reviewing moderator to hard-reject it, but it's better to catch the problem at submission creation time.