reduce code

train.py

@@ -89,8 +89,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     cuda = device.type != 'cpu'
     init_seeds(1 + RANK)
     with torch_distributed_zero_first(RANK):
-        if not data_dict:
-            data_dict = check_dataset(data)  # check
+        data_dict = data_dict or check_dataset(data)  # check if None
     train_path, val_path = data_dict['train'], data_dict['val']
     nc = 1 if single_cls else int(data_dict['nc'])  # number of classes
     names = ['item'] if single_cls and len(data_dict['names']) != 1 else data_dict['names']  # class names