Don't close elements that weren't open

Found by code reading.

Change-Id: I6ebae46e56348d38c595d4c5675f0d3902dee5f7
Reviewed-on: https://gerrit.libreoffice.org/70974
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

sc/source/filter/excel/xelink.cxx

@@ -1226,6 +1226,7 @@ void XclExpCrn::SaveXml( XclExpXmlStream& rStrm )
     ScAddress aAdr( mnScCol, mnScRow, 0);   // Tab number doesn't matter
     for( const auto& rValue : maValues )
     {
+        bool bCloseCell = true;
         if( rValue.has< double >() )
         {
             double fVal = rValue.get< double >();
@@ -1270,9 +1271,13 @@ void XclExpCrn::SaveXml( XclExpXmlStream& rStrm )
         else
         {
             // Empty/blank cell not stored, only aAdr is incremented.
+            bCloseCell = false;
+        }
+        if (bCloseCell)
+        {
+            pFS->endElement(XML_v);
+            pFS->endElement(XML_cell);
         }
-        pFS->endElement( XML_v );
-        pFS->endElement( XML_cell);
         aAdr.IncCol();
     }