Don't die calling outgoing hook if we have no changesets

mercurial/localrepo.py

@@ -1386,7 +1386,9 b' class localrepository(object):'
                         yield chnk
 
             yield changegroup.closechunk()
-            self.hook('outgoing', node=hex(nodes[0]), source=source)
+
+            if nodes:
+                self.hook('outgoing', node=hex(nodes[0]), source=source)
 
         return util.chunkbuffer(gengroup())