subtable corruption is possible

Change-Id: Ifbf4312df583724a22328491bea3b6e05b82418f
(cherry picked from commit 9814cf713c57b211f5632733a853150d1d1e8da9)
Reviewed-on: https://gerrit.libreoffice.org/23767
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
diff --git a/lotuswordpro/qa/cppunit/data/fail/subtable-1.lwp b/lotuswordpro/qa/cppunit/data/fail/subtable-1.lwp
new file mode 100644
index 0000000..3d906ee
--- /dev/null
+++ b/lotuswordpro/qa/cppunit/data/fail/subtable-1.lwp
Binary files differ
diff --git a/lotuswordpro/source/filter/xfilter/xfcell.cxx b/lotuswordpro/source/filter/xfilter/xfcell.cxx
index 7dde717..523bb1a 100644
--- a/lotuswordpro/source/filter/xfilter/xfcell.cxx
+++ b/lotuswordpro/source/filter/xfilter/xfcell.cxx
@@ -89,10 +89,9 @@ void    XFCell::Add(XFContent *pContent)
        Reset();
        m_eValueType = enumXFValueTypeNone;
    }
    if( m_pSubTable )
    if (m_pSubTable)
    {
        assert(false);
        return;
        throw std::runtime_error("subtable already set");
    }
    if (!pContent)
    {