The first changeset cannot have a parent so this would be an empty list.

That should be checked.
Sometimes mercurial uses "0000000000000000000000000000000000000000"

to indicate that the parent is the "null" changeset. Sometimes the

array is empty.

Used a repo with a few changesets. Saw

that it will result into an error if first

changeset will be fetched with cmdline or hgweb.
Added this change and saw that cmdline and hgweb

won't get an error.