I had the error that debootstrap is called with to less values (see image)
After a while I noticed that I had an empty line at the end of my sources.list file. Deleting this line fixed the issue.

It seems that the script reads every line, if it's empty or not.

Two possibility

1. raise a worthy error message, which states the real problem
2. just check if a line is empty and ignore empty lines ...

Reproduce:
Add empty lines to your sources.list for debootstrap and you should run into the error.

https://github.com/ilbers/isar/blob/b6ac71a53eb33b4e777480be557e1220a21c7fa2/meta/recipes-core/isar-bootstrap/isar-bootstrap.inc#L230