error when run deeplab(cityscapes) ValueError: zero-size array to reduction operation minimum which has no identity`

[zyxu1996]

libpng error: Read Error
Exception in thread Thread-7:
Traceback (most recent call last):
File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
self.run()
File "/usr/lib/python2.7/threading.py", line 754, in run
self.__target(*self.__args, **self.__kwargs)
File "/data/xzy/xzy_job/Deformable Convolutional Networks/Deformable-ConvNets/lib/utils/PrefetchingIter.py", line 64, in prefetch_func
self.next_batch[i] = self.iters[i].next()
File "/data/xzy/xzy_job/Deformable Convolutional Networks/Deformable-ConvNets/deeplab/core/loader.py", line 190, in next
self.get_batch_parallel()
File "/data/xzy/xzy_job/Deformable Convolutional Networks/Deformable-ConvNets/deeplab/core/loader.py", line 238, in get_batch_parallel
rst = [multiprocess_result.get() for multiprocess_result in multiprocess_results]
File "/usr/lib/python2.7/multiprocessing/pool.py", line 567, in get
raise self._value
ValueError: zero-size array to reduction operation minimum which has no identity