[JoinActor] adapt join actor to updated code

pypushflow/JoinActor.py

@@ -36,14 +36,18 @@ class JoinActor(AbstractActor):
     def increaseNumberOfThreads(self):
         self.numberOfThreads += 1
 
-    def trigger(self, inData):
-        self.listInData.append(inData)
+    def trigger(self, in_data):
+        if in_data is None:
+            channel = data = None
+        else:
+            channel, data = in_data
+        self.listInData.append(data)
         if len(self.listInData) == self.numberOfThreads:
             newInData = {}
             for data in self.listInData:
                 newInData.update(data)
             for actor in self.listDownStreamActor:
-                actor.trigger(newInData)
+                actor.trigger((channel, data))
 
 
 class JoinUntilStopSignal(AbstractActor):