directaccess: fix uses of commands.status() that don't go through flag parsing

When `commands.commit.post-status` is enabled, after commit/amend,
commands.status() is called without any revs argument, which means that status
gets None instead of an empty list like it would receive if the user had invoked
this on the commandline. With the `experimental.directaccess` config enabled,
this gets passed to `unhidehashlikerevs`, which didn't previously handle None,
but now should.

Differential Revision: https://phab.mercurial-scm.org/D11883

mercurial/scmutil.py

@@ -2197,6 +2197,9 b' def unhidehashlikerevs(repo, specs, hidd'
 
     returns a repo object with the required changesets unhidden
     """
+    if not specs:
+        return repo
+
     if not repo.filtername or not repo.ui.configbool(
         b'experimental', b'directaccess'
     ):