mu4e: lock file may not be created by file watcher
mu4e: lock file may not be created by file watcher

On some OS implementations (e.g. BSD uses kqueue),
`file-notify-add-watch' might not create the file if it doesn't exist.
This patch fixes that error. Arguably, emacs lisp should ensure the same
behaviour exists across each implementation.

hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d