sd-finetuner skip broken images in dataset

[Rexwang8]

Current when the sd-finetuner finds a image in the pvc dataset,

it will

1. Expect it to be a square aspect ratio
2. Expect the image to have a .txt pair with the same name

it will fail the entire process if either condition isn't filled on any image in the dataset.

It would be better if the image is skipped if either error occurs or it uses some form of logic to try and fix it first. (maybe generate a empty txt file or attempt to resize the image itself)