text: Title: Having an error when executing vocoder_preprocess.py
  Body: I'm trying to train vocoder after training synthesizer. But I have this error when executing vocoder_preprocess.py.
  
  ![error](https://user-images.githubusercontent.com/63226383/113960047-cf779300-985e-11eb-991c-b36f6a010fb7.PNG)
  
  So I checked tacotron.py and I realized that the model returns 4 outputs.
  
  ![22](https://user-images.githubusercontent.com/63226383/113960401-69d7d680-985f-11eb-9e7e-9922912b528b.PNG)
  
  but  "model" in run_synthesis.py  is supposed to return 3 outputs(look at the first picture).
  
  I guess that the error is resulted from that part.
  
  How can I solve this problem?
  
  