Small bug in parameter creation.

jedi/parser/tree.py

@@ -745,6 +745,7 @@ def _create_params(parent, argslist_list):
         for end, child in enumerate(children + [None], 1):
             if child is None or child == ',':
                 new_children = children[start:end]
+                if new_children:  # Could as well be comma and then end.
                     if check_python2_nested_param(new_children[0]):
                         continue
                     params.append(Param(new_children, parent))