AttributeError: 'DummyVecEnv' object has no attribute 'render_mode'
### System Info

I'm doing the Deep RL course, I don't know what is happening, something is wrong in the notebook on unit 1: https://colab.research.google.com/github/huggingface/deep-rl-class/blob/master/notebooks/unit1/unit1.ipynb#scrollTo=xMkkkukIBQJM 

when I try to push my Agent to HF Hub I received this error message: AttributeError: 'DummyVecEnv' object has no attribute 'render_mode' 

my code is very similar to the notebook example.

### Who can help?

_No response_

### Information

- [ ] The official example scripts
- [ ] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

Code example: 

import gym

from stable_baselines3 import PPO
from stable_baselines3.common.vec_env import DummyVecEnv
from stable_baselines3.common.env_util import make_vec_env

from huggingface_sb3 import package_to_hub


env_id = "LunarLander-v2"
model_architecture = "PPO"
repo_id = "Felipe474/ppo-LunarLander-v2"  # Change with your repo id, you can't push with mine 😄
commit_message = "Upload PPO LunarLander-v2 trained agent"


eval_env = DummyVecEnv([lambda: gym.make(env_id)])


package_to_hub(model=model, # Our trained model
               model_name=model_name, # The name of our trained model 
               model_architecture=model_architecture, # The model architecture we used: in our case PPO
               env_id=env_id, # Name of the environment
               eval_env=eval_env, # Evaluation Environment
               repo_id=repo_id, # id of the model repository from the Hugging Face Hub (repo_id = {organization}/{repo_name} for instance ThomasSimonini/ppo-LunarLander-v2
               commit_message=commit_message)


### Expected behavior

Successively push agent to HF hub.