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

[AvneeshKhanna]

Traceback (most recent call last):
  File "/home/ubuntu/anaconda3/envs/lstr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/home/ubuntu/anaconda3/envs/lstr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "train.py", line 54, in prefetch_data
    raise e
  File "train.py", line 50, in prefetch_data
    data, ind = sample_data(db, ind)
  File "/home/ubuntu/lstr-custom/LSTR/sample/custom.py", line 71, in sample_data
    return globals()[system_configs.sampling_function](db, k_ind)
  File "/home/ubuntu/lstr-custom/LSTR/sample/custom.py", line 31, in kp_detection
    mask  = np.ones((1, img.shape[0], img.shape[1], 1), dtype=np.bool)
AttributeError: 'NoneType' object has no attribute 'shape'

Hi,
I am getting the above error when loading my custom dataset. I checked, all my files are jpg and in correct directories. However, the error goes away if I keep the sample images provided in the /raw subdirectories as is. Are those sample images not to be replaced?