Empty tensor error after some epochs

I got this type of error message when implemented train_domain_A.py

File "train_domain_A.py", line 70, in losses, generated = model(Variable(data['label']), Variable(data['inst']), File "/home/anaconda3/lib/python3.8/site-packages/torch/nn/modules/module.py", line 722, in _call_impl result = self.forward(*input, **kwargs) File "/home/Desktop/study/Bringing-Old-Photos-Back-to-Life-master/Global/models/pix2pixHD_model_DA.py", line 196, in forward real_old_feat=torch.cat(real_old_feat,0) RuntimeError: There were no tensor arguments to this function (e.g., you passed an empty list of Tensors), but no fallback function is registered for schema aten::_cat. This usually means that this function requires a non-empty list of Tensors. Available functions are [CPU, CUDA, QuantizedCPU, Autograd, Profiler, Tracer, Autocast]

My question is why this type of error arised after some epochs. And my hypothesis is that this occurred accidentally because of data['inst'] are all 0 or 1 (it may happen because I set batchSize to low number)

Please tell me your insights, thank you.