ValueError: need at least one array to concatenate

INFO:test2:====> Epoch: 200 [2023-08-26 18:18:25] | (0:00:20.367071)
INFO:test2:Training is done. The program is closed.
INFO:test2:saving final ckpt:Success.
Traceback (most recent call last):
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\gradio\routes.py", line 321, in run_predict
output = await app.blocks.process_api(
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\gradio\blocks.py", line 1006, in process_api
result = await self.call_function(fn_index, inputs, iterator, request)
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\gradio\blocks.py", line 859, in call_function
prediction = await anyio.to_thread.run_sync(
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\anyio\to_thread.py", line 31, in run_sync
return await get_asynclib().run_sync_in_worker_thread(
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\anyio_backends_asyncio.py", line 937, in run_sync_in_worker_thread
return await future
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\anyio_backends_asyncio.py", line 867, in run
result = context.run(func, *args)
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\runtime\lib\site-packages\gradio\utils.py", line 408, in async_iteration
return next(iterator)
File "C:\Users\Catalin\Desktop\RVC0813AMD_Intel\RVC0813AMD_Intel\infer-web.py", line 1283, in train1key
big_npy = np.concatenate(npys, 0)
File "<array_function internals>", line 180, in concatenate
ValueError: need at least one array to concatenate

Start in infer-web.py at line 1283, where train1key passes npys to np.concatenate after training completes. Trace how npys is populated and identify why it can be empty for this training run. Reproduce the reported workflow and verify the completed training path no longer raises this ValueError.