added a none check for original received data

Signed-off-by: Ebbe Baß <ebbe.bass>

server/app.py

@@ -120,7 +120,9 @@ def mqtt_publisher(ti_receiver):
             artNetPacket = artNet.readPacket()
             # Make sure we actually *have* a packet
             if ti_receiver.poll():
-                tube_index = literal_eval(ti_receiver.recv())
+                ti_data = ti_receiver.recv()
+                if ti_data is not None:
+                    tube_index = literal_eval(ti_data)
                     if artNetPacket is not None:
                         #Checks to see if the current packet is for the specified DMX Universe
                         dmxPacket = artNetPacket.data