fix getchild for directory

src/allmydata/web/directory.py

@@ -116,12 +116,15 @@ class DirectoryNodeHandler(ReplaceMeMixin, Resource, object):
         """
         Dynamically create a child for the given request and name
         """
-        # XXX can we do this with putChild() instead? (i.e. does it
-        # HAVE to be dynamic?)
-        if name is None:
-            name = get_arg(req, "uri")
-        d = self.node.get(name.decode('utf8'))
+        if self.name is None:
+            return self
+        name = name.decode("utf-8")
+        if not name:
+            raise EmptyPathnameComponentError()
+        d = self.node.get(name)
         d.addBoth(self._got_child, req, name)
+        # got_child returns a handler resource: FileNodeHandler or
+        # DirectoryNodeHandler
         return d
 
     def _got_child(self, node_or_failure, req, name):