fix warning

git-svn-id: http://svn.osgeo.org/qgis/trunk@15516 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: jef

src/core/qgsvectorlayer.h

@@ -49,7 +49,7 @@ class QgsRectangle;
 class QgsVectorLayerJoinBuffer;
 class QgsFeatureRendererV2;
 class QgsDiagramRendererV2;
-class QgsDiagramLayerSettings;
+struct QgsDiagramLayerSettings;
 
 typedef QList<int> QgsAttributeList;
 typedef QSet<int> QgsFeatureIds;