Improve missing toolcall exception (#614)

src/smolagents/models.py

@@ -132,6 +132,7 @@ def parse_json_if_needed(arguments: Union[str, dict]) -> Union[str, dict]:
 
 
 def parse_tool_args_if_needed(message: ChatMessage) -> ChatMessage:
+    if message.tool_calls is not None:
         for tool_call in message.tool_calls:
             tool_call.function.arguments = parse_json_if_needed(tool_call.function.arguments)
     return message

tests/test_models.py

@@ -107,6 +107,11 @@ class ModelTests(unittest.TestCase):
         output = model(messages, stop_sequences=["great"]).content
         assert output == "Hello! How can"
 
+    def test_parse_tool_args_if_needed(self):
+        original_message = ChatMessage(role="user", content=[{"type": "text", "text": "Hello!"}])
+        parsed_message = models.parse_tool_args_if_needed(original_message)
+        assert parsed_message == original_message
+
     def test_parse_json_if_needed(self):
         args = "abc"
         parsed_args = parse_json_if_needed(args)