simplify SimulationResult::flatVector

Device/Histo/SimulationResult.cpp

@@ -52,8 +52,7 @@ size_t SimulationResult::size() const
 
 std::vector<double> SimulationResult::flatVector(Coords units) const
 {
-    std::unique_ptr<Datafield> f(datafield(units));
-    return f->flatVector();
+    return m_data->flatVector();
 }
 
 Datafield* SimulationResult::datafield(Coords units) const