In the classic layout an undo-send entry carries no login, and since
5f0669eb a draft opened without one is no longer stamped with the
active login. When the user switched to another login inside the undo
window and then clicked Undo, the send was cancelled on the right
server, but the reopened draft's first save ran through the login now
active and removed the old version by id there, where an unrelated
message can have the same id. The undo toast now remembers the login
that was active when the message was sent and reopens the draft
through it.
Linus Rath
b80764264a