D3140: rebase: remove unnecessary and incorrect handling of nullid

[martinvonz (Martin von Zweigbergk)]

martinvonz added a comment.


  In https://phab.mercurial-scm.org/D3140#50376, @quark wrote:
  
  > Hmm... maybe just remove it.
  
  
  Done.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D3140

To: martinvonz, #hg-reviewers, quark
Cc: quark, mercurial-devel