fix: Fix error messages with malformed gemini call (#3865)

letta/llm_api/google_vertex_client.py

@@ -303,11 +303,11 @@ class GoogleVertexClient(LLMClientBase):
             for candidate in response.candidates:
                 content = candidate.content
 
-                if content.role is None or content.parts is None:
+                if content is None or content.role is None or content.parts is None:
                     # This means the response is malformed like MALFORMED_FUNCTION_CALL
                     # NOTE: must be a ValueError to trigger a retry
                     if candidate.finish_reason == "MALFORMED_FUNCTION_CALL":
-                        raise ValueError(f"Error in response data from LLM: {candidate.finish_message[:350]}...")
+                        raise ValueError(f"Error in response data from LLM: {candidate.finish_reason}...")
                     else:
                         raise ValueError(f"Error in response data from LLM: {response_data}")