Ground-truth of validation dataset may have leaked when training

[Fangkang515]

Thanks for your work.

When using Mega-NeRF and GP-NeRF, I have noticed that the validation set might have been inadvertently included in the training set (in this issue). It seems that this issue has also been carried over to GP-NeRF.

I'm not certain if I may have overlooked an important part of the code, but if there are any errors, please feel free to point out my mistakes.

[zyqz97]

Refer to this issue