scaling without specified view is broken

[Phlya]

It runs, but n_bp2 column is all empty, I think it's because we don't provide the chromsizes from the pairs header here...
https://github.com/open2c/pairtools/blob/83ad59199b4d89aabfa72331b5e89d52b7786b19/pairtools/cli/scaling.py#L94C1-L94C25

Should be an easy fix if so