This can happen when the group calculation is disabled and falls
back to non-group calculations.  And we only care about the first
entry in case of non-group calculation of grouped cells.

Change-Id: I545980acf8e35b4d0504aa2a77f86bdc85799e29
Reviewed-on: https://gerrit.libreoffice.org/30738Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>