text: Title: 预处理数据集出现如下错误
  Body: 做预处理数据集时出现如下错误：
  E:\Miniconda3\envs\mockingbird\MockingBird-main>python pre.py E:\Miniconda3\envs\mockingbird\MockingBird-main -d aidatatang_200zh -n 1
  Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  Using data from:
      E:\Miniconda3\envs\mockingbird\MockingBird-main\aidatatang_200zh\corpus\train
  aidatatang_200zh:   0%|                                                                  | 0/547 [00:00<?, ?speakers/s]Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  Ignored unknown kwarg option normalize
  aidatatang_200zh: 100%|████████████████████████████████████████████████████████| 547/547 [01:17<00:00,  7.03speakers/s]
  The dataset consists of 0 utterances, 0 mel frames, 0 audio timesteps (0.00 hours).
  Traceback (most recent call last):
    File "E:\Miniconda3\envs\mockingbird\MockingBird-main\pre.py", line 72, in <module>
      preprocess_dataset(**vars(args))
    File "E:\Miniconda3\envs\mockingbird\MockingBird-main\models\synthesizer\preprocess.py", line 101, in preprocess_dataset
      print("Max input length (text chars): %d" % max(len(m[5]) for m in metadata))
  ValueError: max() arg is an empty sequence
  
  ![3c415e817f0c9484ccbebf3bbfce394](https://github.com/babysor/MockingBird/assets/157026872/31f96d33-151a-4919-8f7c-62d4e3d4a037)
  
  请大神们给予帮助！！！