AttributeError: 'NoneType' object has no attribute 'unsqueeze'

[WanyingMo]

Importing module 'gym_38' (/apps/IsaacGym_Preview_4_Package/isaacgym/python/isaacgym/_bindings/linux-x86_64/gym_38.so)
Setting GYM_USD_PLUG_INFO_PATH to /apps/IsaacGym_Preview_4_Package/isaacgym/python/isaacgym/_bindings/linux-x86_64/usd/plugInfo.json
PyTorch version 1.13.0+cu117
Device count 1
/apps/IsaacGym_Preview_4_Package/isaacgym/python/isaacgym/_bindings/src/gymtorch
Using /.cache/torch_extensions/py38_cu117 as PyTorch extensions root...
Emitting ninja build file /.cache/torch_extensions/py38_cu117/gymtorch/build.ninja...
Building extension module gymtorch...
Allowing ninja to set a default number of workers... (overridable by setting the environment variable MAX_JOBS=N)
ninja: no work to do.
Loading extension module gymtorch...
Setting seed: 1
20
0.019999999552965164
Not connected to PVD
+++ Using GPU PhysX
Physics Engine: PhysX
Physics Device: cuda:0
GPU Pipeline: enabled

---

Start creating ground...
Converting heightmap to trimesh...
Created 12920000 vertices
Created 25825602 triangles
Adding trimesh to simulation...
Trimesh added
Finished creating ground. Time taken 53.78 s

---

Creating env...
100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 6144/6144 [00:01<00:00, 5705.90it/s]
/anaconda3/envs/parkour/lib/python3.8/site-packages/torch/functional.py:504: UserWarning: torch.meshgrid: in an upcoming release, it will be required to pass the indexing argument. (Triggered internally at ../aten/src/ATen/native/TensorShape.cpp:3190.)
return _VF.meshgrid(tensors, **kwargs) # type: ignore[attr-defined]
Using MLP and Priviliged Env encoder ActorCritic structure
ActorCritic.init got unexpected arguments, which will be ignored: ['continue_from_last_std', 'priv_encoder_dims', 'rnn_hidden_size', 'rnn_num_layers', 'rnn_type', 'tanh_encoder_output']
Traceback (most recent call last):
File "train.py", line 40, in
train(args)
File "train.py", line 35, in train
ppo_runner.learn(num_learning_iterations=train_cfg.runner.max_iterations, init_at_random_ep_len=True)
File "/Desktop/extreme-parkour-main/rsl_rl/rsl_rl/runners/on_policy_runner.py", line 168, in learn_RL
total_rew = self.alg.process_env_step(rewards, dones, infos)
File "/Desktop/extreme-parkour-main/rsl_rl/rsl_rl/algorithms/ppo.py", line 170, in process_env_step
self.transition.rewards += self.gamma * torch.squeeze(self.transition.values * infos['time_outs'].unsqueeze(1).to(self.device), 1)
AttributeError: 'NoneType' object has no attribute 'unsqueeze'

I was running the project, everything was fine until this error suddenly came out. I have run this project for several times, and already got some checkpoints successfully. Did anyone meet this problem? Thanks!