Fix crash when saving categorized symbology

src/core/symbology-ng/qgscategorizedsymbolrendererv2.cpp

@@ -724,7 +724,7 @@ QDomElement QgsCategorizedSymbolRendererV2::save( QDomDocument& doc )
   QgsSymbolV2Map symbols;
   QDomElement catsElem = doc.createElement( "categories" );
   QgsCategoryList::const_iterator it = mCategories.constBegin();
-  for ( ; it != mCategories.end(); ++it )
+  for ( ; it != mCategories.constEnd(); ++it )
   {
     const QgsRendererCategoryV2& cat = *it;
     QString symbolName = QString::number( i );