fix crash on export of ooo88740-1.odt to .docx

use similar logic as AttributeOutputBase::FormatCharBorder

Change-Id: I71c4aa28c2495fd4a357fd62568aaa49e918da5c

sw/source/filter/ww8/docxsdrexport.cxx

@@ -1303,24 +1303,47 @@ void DocxSdrExport::writeOnlyTextOfFrame(sw::Frame* pParentFrame)
     m_pImpl->m_bFrameBtLr = false;
 }
 
-void DocxSdrExport::writeBoxItemLine(const SvxBoxItem& rBoxItem)
+void DocxSdrExport::writeBoxItemLine(const SvxBoxItem& rBox)
 {
+    const editeng::SvxBorderLine* pBorderLine = 0;
+
+    if( rBox.GetTop() )
+    {
+       pBorderLine = rBox.GetTop();
+    }
+    else if( rBox.GetLeft() )
+    {
+       pBorderLine = rBox.GetLeft();
+    }
+    else if( rBox.GetBottom() )
+    {
+       pBorderLine = rBox.GetBottom();
+    }
+    else if( rBox.GetRight() )
+    {
+       pBorderLine = rBox.GetRight();
+    }
+
+    if (!pBorderLine)
+    {
+        return;
+    }
+
     sax_fastparser::FSHelperPtr pFS = m_pImpl->m_pSerializer;
-    const editeng::SvxBorderLine* pTop = rBoxItem.GetTop();
-    double fConverted(editeng::ConvertBorderWidthToWord(pTop->GetBorderLineStyle(), pTop->GetWidth()));
+    double fConverted(editeng::ConvertBorderWidthToWord(pBorderLine->GetBorderLineStyle(), pBorderLine->GetWidth()));
     OString sWidth(OString::number(TwipsToEMU(fConverted)));
     pFS->startElementNS(XML_a, XML_ln,
                         XML_w, sWidth.getStr(),
                         FSEND);
 
     pFS->startElementNS(XML_a, XML_solidFill, FSEND);
-    OString sColor(msfilter::util::ConvertColor(pTop->GetColor()));
+    OString sColor(msfilter::util::ConvertColor(pBorderLine->GetColor()));
     pFS->singleElementNS(XML_a, XML_srgbClr,
                          XML_val, sColor,
                          FSEND);
     pFS->endElementNS(XML_a, XML_solidFill);
 
-    if (drawing::LineStyle_DASH == pTop->GetBorderLineStyle()) // Line Style is Dash type
+    if (drawing::LineStyle_DASH == pBorderLine->GetBorderLineStyle()) // Line Style is Dash type
         pFS->singleElementNS(XML_a, XML_prstDash, XML_val, "dash", FSEND);
 
     pFS->endElementNS(XML_a, XML_ln);