tdf#132278 crash after opening an old file

regression from
    commit 7282014e362a1529a36c88eb308df8ed359c2cfa
    tdf#50916 Makes numbers of columns dynamic.

Change-Id: I7a37631094b91f4859326db054f285daa8dccbb8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/92740
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/sc/source/core/data/dociter.cxx b/sc/source/core/data/dociter.cxx
index 85be65c..eb11099 100644
--- a/sc/source/core/data/dociter.cxx
+++ b/sc/source/core/data/dociter.cxx
@@ -325,7 +325,8 @@
    ScTable* pTab = rDoc.FetchTable(nTab);
    if (!pTab)
        return nullptr;

    if (nCol >= pTab->GetAllocatedColumnsCount())
        return nullptr;
    return &pTab->aCol[nCol].maCells;
}