[PythonActor] if data is None, set to it to dict

pypushflow/PythonActor.py

@@ -42,6 +42,8 @@ class WorkflowException(Exception):
     def __init__(self, errorMessage="", traceBack="", data={}, msg=None):
         super(WorkflowException, self).__init__(msg)
         self.errorMessage = errorMessage
+        if data is None:
+            data = {}
         self.data = data
         self.traceBack = traceBack