Since only elements from nOffset up to nEnd are iterated, then the difference
is not just nEnd but (nEnd-nOffset).
Without this, ScColumn::HandleRefArrayForParallelism() skips some cells
and e.g. fdo#77750-1 asserts in ScFormulaCell::MaybeInterpret().

Change-Id: I4d595e9faff51f08bf074d549185c24aa00d8a45
Reviewed-on: https://gerrit.libreoffice.org/55488Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>