fixed error with claude

gpt_researcher/llm_provider/anthropic/anthropic.py

@@ -14,7 +14,7 @@ def __init__(
     ):
         self.model = model
         self.temperature = temperature
-        self.max_tokens = max_tokens
+        self.max_tokens = max_tokens if max_tokens else 4096
         self.api_key = self.get_api_key()
         self.llm = self.get_llm_model()
 
@@ -37,6 +37,7 @@ def get_llm_model(self):
             model=self.model,
             temperature=self.temperature,
             max_tokens=self.max_tokens,
+            max_tokens_to_sample=4096,
             api_key=self.api_key
         )