app/calendar: fix edge case with +calendar/quit
app/calendar: fix edge case with +calendar/quit

The user can open the calendar directly, with `M-x
cfw:open-calendar-buffer`, which sidesteps the workspace init logic in
=calendar. This fixes +calendar/quit so it can deal with this use case.

Mentioned in #4019

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