Fixed Build without OpenVolumeMesh (Thanks to Matthias Moeller for the patch)

MultiObjectPropertyModel.cc

@@ -51,7 +51,10 @@
 
 #include "PropertyModelFactory.hh"
 #include "OpenMesh/OMPropertyModel.hh"
+
+#ifdef ENABLE_OPENVOLUMEMESH
 #include "OpenVolumeMesh/OVMPropertyModelT.hh"
+#endif
 
 MultiObjectPropertyModel::MultiObjectPropertyModel(const QStringList& res, QObject *parent) :
     PropertyModel(parent), restriction(res), datatypes(supportedDataTypes()), widget(0)