hgweb: do not access first changeset with a string

There is not reason not to use an int

mercurial/hgweb/webutil.py

@@ -66,7 +66,7 b' def revnavgen(pos, pagelen, limit, nodef'
 
     navafter.append(("tip", "tip"))
     try:
-        navbefore.insert(0, ("(0)", hex(nodefunc('0').node())))
+        navbefore.insert(0, ("(0)", hex(nodefunc(0).node())))
     except error.RepoError:
         pass