Hi @ngtiendong, welcome to the forum 
When you say “I have the same issue”, do you mean that you are also setting initial_value of some slot in your domain while also using conversation_start: true for some of your rules? If yes, then the fixing PR should help for the time being.
If what you mean is that you’re just getting the same error as @noman, then could you, please, share your rules and stories (at least the ones mentioned in the error message), and possibly also your domain file? Which version of Rasa Open Source are you using?