Add fallback token limit in llm.utils.create_chat_completion (#4839)

Co-authored-by: Reinier van der Leer <github@pwuts.nl>

autogpt/llm/utils/__init__.py

@@ -115,6 +115,8 @@ def create_chat_completion(
         model = prompt.model.name
     if temperature is None:
         temperature = config.temperature
+    if max_tokens is None:
+        max_tokens = OPEN_AI_CHAT_MODELS[model].max_tokens - prompt.token_length
 
     logger.debug(
         f"{Fore.GREEN}Creating chat completion with model {model}, temperature {temperature}, max_tokens {max_tokens}{Fore.RESET}"