fix a bug with 2 executions

src/jflow/workflow.py

@@ -183,6 +183,9 @@ class Workflow(threading.Thread):
                     # add the component
                     self.components.append(cmpt_object)
                 elif not self.component_nameids_is_init and not self.dynamic_component_present:
+                    if self._component_is_duplicated(cmpt_object):
+                        raise ValueError("Component " + cmpt_object.__class__.__name__ + " with prefix " + 
+                                            cmpt_object.prefix + " already exist in this pipeline!")
                     self.components.append(cmpt_object)
                 else:
                     if self._component_is_duplicated(cmpt_object):