fdo#79822 : Crash:LO Crashes while Saving the DOCX containing smartart

Decription :
- Docx file contain smartart and it was created in MS word 2007.
- MS word 2007 does not create any drawing.xml for smartart
- So in DocxSdrExport::writeDiagram() diagramDrawing was not set in this case.
- File crashing at diagramDrawing[0] >>= drawingDom as diagramDrawing is empty.

Change-Id: I6bc38e702f731ad8074b562572fd50f2e29a41b7
Reviewed-on: https://gerrit.libreoffice.org/9706Tested-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
(cherry picked from commit 17855092)

sw/qa/extras/ooxmlexport/ooxmlexport.cxx

@@ -3468,6 +3468,16 @@ DECLARE_OOXMLEXPORT_TEST(testWordArtWithinDraingtool, "testWordArtWithinDraingto
     assertXPath(pXmlDoc,"/w:document[1]/w:body[1]/w:p[1]/w:r[3]/mc:AlternateContent[1]/mc:Choice[1]/w:drawing[1]/wp:inline[1]/a:graphic[1]/a:graphicData[1]/wps:wsp[1]/wps:txbx[1]/w:txbxContent[1]",1);
 }
 
+DECLARE_OOXMLEXPORT_TEST(testfdo79822, "fdo79822.docx")
+{
+    /* File getting crash while saving in LO.
+     * The Docx contain smartart and the file was created in ms word 2007
+     */
+    xmlDocPtr pXmlDoc = parseExport("word/document.xml");
+    if (!pXmlDoc)
+        return;
+}
+
 #endif
 
 CPPUNIT_PLUGIN_IMPLEMENT();

sw/source/filter/ww8/docxsdrexport.cxx

@@ -945,12 +945,14 @@ void DocxSdrExport::writeDiagram(const SdrObject* sdrObject, const SwFrmFmt& rFr
         else if (propName == "OOXColor")
             propList[nProp].Value >>= colorDom;
         else if (propName == "OOXDrawing")
+        {
             propList[nProp].Value >>= diagramDrawing;
+            diagramDrawing[0] >>= drawingDom; // if there is OOXDrawing property then set drawingDom here only.
+        }
         else if (propName == "OOXDiagramDataRels")
             propList[nProp].Value >>= xDataRelSeq;
     }
 
-    diagramDrawing[0] >>= drawingDom;
     // check that we have the 4 mandatory XDocuments
     // if not, there was an error importing and we won't output anything
     if (!dataDom.is() || !layoutDom.is() || !styleDom.is() || !colorDom.is())