ADD: set m_ExecuteDone = True in WriteOutput()

Modules/Wrappers/ApplicationEngine/src/otbWrapperApplication.cxx

@@ -943,6 +943,10 @@ void Application::WriteOutput()
     AddProcess(multiWriter, progressId.str());
     multiWriter->Update();
   }
+  
+  // Set the flag m_ExecuteDone since the pipeline has been successfully executed
+  // This enables to access output parameters after WriteOutput()
+  m_ExecuteDone = true;
 }
 
 int Application::ExecuteAndWriteOutput()