fix NULL dereference

Only the Clang tinderbox fails here for some reason, but e.g. code
in ww8par5.cxx check for non-NULL too, so it's apparently possible.

Change-Id: I985445f7727560116813aacbca40c0e7c0a4863f

sw/source/filter/ww8/docxattributeoutput.cxx

@@ -2006,7 +2006,8 @@ void DocxAttributeOutput::TableVerticalCell( ww8::WW8TableNodeInfoInner::Pointer
         if (aPam.GetPoint()->nNode.GetNode().IsTxtNode())
         {
             const SwTxtNode& rTxtNode = (const SwTxtNode&)aPam.GetPoint()->nNode.GetNode();
-            const SwAttrSet* pAttrSet = rTxtNode.GetpSwAttrSet();
+            if( const SwAttrSet* pAttrSet = rTxtNode.GetpSwAttrSet())
+            {
                 const SvxCharRotateItem& rCharRotate = pAttrSet->GetCharRotate();
                 if (rCharRotate.GetValue() == 900)
                 {
@@ -2015,6 +2016,7 @@ void DocxAttributeOutput::TableVerticalCell( ww8::WW8TableNodeInfoInner::Pointer
                 }
             }
         }
+    }
 
     const SwWriteTableRows& aRows = m_pTableWrt->GetRows( );
     SwWriteTableRow *pRow = aRows[ pTableTextNodeInfoInner->getRow( ) ];