hgweb: ignore filtered revision in revnav This changeset checks that a revision is known before adding it to the navigation. This will prevent traceback on filtered repository. This changeset result in an incorrect behaviors, Navigation link may be dropped without any replacement. However this bad navigation generation is much better than a crash

  $ "$TESTDIR/hghave" execbit || exit 80

  $ hg init repo
  $ cd repo
  $ echo foo > foo
  $ chmod 644 foo
  $ hg ci -qAm '644'

  $ chmod 755 foo
  $ hg ci -qAm '755'

reverting to rev 0

  $ hg revert -a -r 0
  reverting foo
  $ hg st
  M foo
  $ hg diff --git
  diff --git a/foo b/foo
  old mode 100755
  new mode 100644

  $ cd ..