add check for cfg.policy in force_cpu line

src/lerobot/scripts/lerobot_train.py

@@ -263,7 +263,8 @@ def train(cfg: TrainPipelineConfig, accelerator: Accelerator | None = None):
         ddp_kwargs = DistributedDataParallelKwargs(find_unused_parameters=True)
         # Accelerate auto-detects the device based on the available hardware and ignores the policy.device setting.
         # Force the device to be CPU when policy.device is set to CPU.
-        force_cpu = cfg.policy.device == "cpu"
+        # Note (maractin): cfg.policy may be None before validate() fully loads from pretrained_path
+        force_cpu = cfg.policy is not None and cfg.policy.device == "cpu"
         accelerator = Accelerator(
             step_scheduler_with_optimizer=False,
             kwargs_handlers=[ddp_kwargs],