revset: fix crash by repo.revs('%d', tip + 1)
IndexError shouldn't be raised from a revset predicate. The error message
is copied from scmutil.revsymbol().
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}