submit-emacs-patch creates a new message and immediately inserts new
lines without first moving the point to the message body. This
doesn't work with notmuch (and its notmuch-user-agent symbol) because
the point starts in the headers and nothing in Emacs specifies that
the mua should move point to the body automatically.
* lisp/mail/emacsbug.el (submit-emacs-patch): Make sure point is in
the body before inserting new lines (bug#55571).
959d041677