ValueError when running "run_video.py"

[SAIL-LAB155]

Hello.
When I am running the webcam demo with "python run_video.py -c configs/mpii/config_blazepose_mpii_pushup_heatmap_bce_regress_huber.json -m blazepose_pushup_v1.h5 -v webcam --confidence 0.3", an error occurs:

**Traceback (most recent call last):
File "run_video.py", line 45, in
model = trainer.load_model(config, args.model)
File "/home/hkuit155/Desktop/tf-blazepose/src/trainers/blazepose_trainer.py", line 162, in load_model
model.compile()
File "/home/hkuit155/anaconda3/lib/python3.7/site-packages/tensorflow_core/python/training/tracking/base.py", line 457, in _method_wrapper
result = method(self, *args, **kwargs)
File "/home/hkuit155/anaconda3/lib/python3.7/site-packages/tensorflow_core/python/keras/engine/training.py", line 446, in compile
self._compile_weights_loss_and_weighted_metrics()
File "/home/hkuit155/anaconda3/lib/python3.7/site-packages/tensorflow_core/python/training/tracking/base.py", line 457, in _method_wrapper
result = method(self, *args, kwargs)
File "/home/hkuit155/anaconda3/lib/python3.7/site-packages/tensorflow_core/python/keras/engine/training.py", line 1592, in _compile_weights_loss_and_weighted_metrics
self.total_loss = self._prepare_total_loss(masks)
File "/home/hkuit155/anaconda3/lib/python3.7/site-packages/tensorflow_core/python/keras/engine/training.py", line 1691, in _prepare_total_loss
raise ValueError('The model cannot be compiled '
ValueError: The model cannot be compiled because it has no loss to optimize.

It seems that the model needs to be trained before running with webcam. And the error appears when training begins.
Are there any solutions for it? I am looking forward to your reply. Thans you so much.