fftester: subtable is a subtable of itself

Change-Id: I9de983e3c9436ab3a37d3482b0f18f04c7cdaaca

lotuswordpro/source/filter/xfilter/xfcell.hxx

@@ -141,6 +141,8 @@ public:
      */
     virtual void    ToXml(IXFStream *pStrm) override;
 
+    const XFTable*  GetSubTable() const { return m_pSubTable; }
+
 private:
     XFRow          *m_pOwnerRow;
     XFTable        *m_pSubTable;

lotuswordpro/source/filter/xfilter/xftable.cxx

@@ -91,6 +91,13 @@ void XFTable::AddRow(XFRow *pRow)
 {
     assert(pRow);
 
+    for (sal_Int32 i = 0; i < pRow->GetCellCount(); ++i)
+    {
+        XFCell* pFirstCell = pRow->GetCell(i + 1); //starts at 1, not 0
+        if (pFirstCell->GetSubTable() == this)
+            throw std::runtime_error("table is a subtable of itself");
+    }
+
     int row = pRow->GetRow();
 
     if( row<1 )