Removing self from post users while editing the post fails gracefully

[Marri]

Report from Anya

.... lmfao funny thing I just did. I was editing one of Sage's self threads (the top post) that I was invited on, but hadn't actually joined. I took myself off the invite but also added something to the thread description, then pressed 'save'. the site was like "uhhhhh? error!" and the result was it saved the subtraction of me from the thread, but not the description edit. which is probably correct but the site was very confused :p

This should at minimum not crash and preferably have an actually-considered method of being handled.