TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType #4

Hello,

I get the above error when I tried to execute ./codes/official_metrics/evaluate.py

More details here:

[root@localhost TecoGAN-PyTorch]# python3 ./codes/official_metrics/evaluate.py --model TecoGAN_BD_iter500000
Traceback (most recent call last):
File "/root/TecoGAN-PyTorch/codes/official_metrics/metrics.py", line 21, in
if not os.path.exists(FLAGS.output):
File "/usr/lib64/python3.6/genericpath.py", line 19, in exists
os.stat(path)
TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType
Traceback (most recent call last):
File "/root/TecoGAN-PyTorch/codes/official_metrics/metrics.py", line 21, in
if not os.path.exists(FLAGS.output):
File "/usr/lib64/python3.6/genericpath.py", line 19, in exists
os.stat(path)
TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType