Crash fix.

Though getTheme() is not supposed to be returning NULL.
It seems like doing that sometimes.

oox/source/ppt/slidefragmenthandler.cxx

@@ -174,7 +174,9 @@ SlideFragmentHandler::~SlideFragmentHandler() throw()
 
     case PPT_TOKEN( bgRef ):            // a:CT_StyleMatrixReference
         {
-            const FillProperties *pFillProperties = mpSlidePersistPtr->getTheme()->getFillStyle( rAttribs.getInteger( XML_idx, -1 ) );
+            const FillProperties *pFillProperties = NULL;
+            if( mpSlidePersistPtr->getTheme() )
+                pFillProperties = mpSlidePersistPtr->getTheme()->getFillStyle( rAttribs.getInteger( XML_idx, -1 ) );
             FillPropertiesPtr pFillPropertiesPtr( pFillProperties ? new FillProperties( *pFillProperties ) : new FillProperties() );
             ContextHandlerRef ret = new ColorContext( *this, mpSlidePersistPtr->getBackgroundColor() );
             mpSlidePersistPtr->setBackgroundProperties( pFillPropertiesPtr );