EndListeningContext holds BroadcasterStoreType iterators in its
ColumnBlockPositionSet and collects broadcasters to purge them at the
end. Removing broadcasters from ScColumn::maBroadcasters in between
invalidates the iterators. Hence calling the "normal" EndListening()
that removes a broadcaster when all listeners are gone while an
EndListeningContext is in use is bad.

Change-Id: Ibdd88469e91e6173ceff1f391c23ef7cb7c6f596
(cherry picked from commit e4a8ae0b)
Reviewed-on: https://gerrit.libreoffice.org/18615Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>