add a clearDocumentHandler for null document handler case

Change-Id: I661a2fd5381013056c69b379792560aed7121214

include/oox/core/fastparser.hxx

@@ -78,6 +78,8 @@ public:
     void                setDocumentHandler(
                             const css::uno::Reference< css::xml::sax::XFastDocumentHandler >& rxDocHandler );
 
+    void                clearDocumentHandler();
+
     /** Parses the passed SAX input source.
         @param bCloseStream  True = closes the stream in the input source after parsing.
         @throws css::xml::sax::SAXException

oox/source/core/fastparser.cxx

@@ -107,6 +107,13 @@ void FastParser::setDocumentHandler( const Reference< XFastDocumentHandler >& rx
     mxParser->setFastDocumentHandler( rxDocHandler );
 }
 
+void FastParser::clearDocumentHandler()
+{
+    if (!mxParser.is())
+        return;
+    mxParser->setFastDocumentHandler(nullptr);
+}
+
 void FastParser::parseStream( const InputSource& rInputSource, bool bCloseStream )
 {
     // guard closing the input stream also when exceptions are thrown

oox/source/core/xmlfilterbase.cxx

@@ -211,7 +211,7 @@ XmlFilterBase::~XmlFilterBase()
     // the following implicit destruction chain of ~XmlFilterBaseImpl, but in that
     // case it's member RelationsMap maRelationsMap will be destroyed, but maybe
     // still be used by ~FragmentHandler -> crash.
-    mxImpl->maFastParser.setDocumentHandler( nullptr );
+    mxImpl->maFastParser.clearDocumentHandler();
 }
 
 void XmlFilterBase::checkDocumentProperties(const Reference<XDocumentProperties>& xDocProps)