bug#63835: 29.0.60; gnus-icalendar--update-org-event fails if org buffer narrowed

[Kevin Brubeck Unhammer]

When running gnus-icalendar--update-org-event (by clicking the [Update
Org Entry] button on a calender invite email), if the org buffer
containing the previously recorded event is narrowed such that the event
is out of view, the line 

                  (re-search-forward "^\\*+ " (line-end-position))

may fail and the function error instead of updating the event
completely. Seems like changing 

      (with-current-buffer (find-file-noselect file)
          (with-slots (uid summary description organizer location recur

to
      (with-current-buffer (find-file-noselect file)
        (save-restriction
          (widen)
          (with-slots (uid summary description organizer location recur

in the same function fixes it.