milvus cannot add to the database when passing the list message

[knysfh]

🐛 Describe the bug

When using Milvus, it is unable to insert into the database when passing in List[Dict], but it works when using strings. Below is the reproduction example:

import os
from mem0 import Memory

os.environ["OPENAI_API_KEY"] = "xxxx-xxxx-xxxx"

config = {
    "embedder": {
            "provider": "huggingface",
            "config": {"huggingface_base_url": "http://xx.xx.xx.xx:xx/v1"},
        },
    "llm": {
            "provider": "openai",
            "config": {
                "model": "gpt-4o",
            },
        },
    "vector_store": {
        "provider": "milvus",
        "config": {
            "collection_name": "test",
            "embedding_model_dims": "1024",
            "url": "http://localhost:19530",
        }
    }
}

m = Memory.from_config(config)
messages = [
    {"role": "user", "content": "I'm planning to watch a movie tonight. Any recommendations?"},
    {"role": "assistant", "content": "How about a thriller movies? They can be quite engaging."},
    {"role": "user", "content": "I’m not a big fan of thriller movies but I love sci-fi movies."},
    {"role": "assistant", "content": "Got it! I'll avoid thriller recommendations and suggest sci-fi movies in the future."}
]
m.add(messages, user_id="alice", metadata={"category": "movies"})
print(m.get_all(user_id="alice"))

# Output:
# {'results': []}

for i in messages:
    m.add(i["content"], user_id="alice", metadata={"category": "movies"})
print(m.get_all(user_id="alice"))

# Output:
# {'results': [{'id': '44fcb6e0-6387-4c8d-b3ee-67d2e47b7e56', 'memory': 'Loves sci-fi movies', 'hash': '1110b1af77367917ea2022355a16f187', 'metadata': {'category': 'movies'}, 'created_at': '2025-06-16T05:33:19.842249-07:00', 'updated_at': None, 'user_id': 'alice'}, {'id': '5273f81c-7ada-4dab-b6f8-f906cec75086', 'memory': 'Planning to watch a movie tonight', 'hash': 'bf55418607cfdca4afa311b5fd8496bd', 'metadata': {'category': 'movies'}, 'created_at': '2025-06-16T05:33:19.811694-07:00', 'updated_at': None, 'user_id': 'alice'}, {'id': 'f11f77ed-03d7-4f2c-815f-67d9844d36c3', 'memory': 'Not a big fan of thriller movies', 'hash': '028dfab4483f28980e292f62578d3293', 'metadata': {'category': 'movies'}, 'created_at': '2025-06-16T05:33:19.830723-07:00', 'updated_at': '2025-06-16T05:33:39.545126-07:00', 'user_id': 'alice'}]}