another parser issue, very much related to the last one. sometimes a None element was used as a token.fixes #418

jedi/parser/representation.py

@@ -1073,7 +1073,8 @@ isinstance(c, (tokenize.Token, Operator)) else unicode(c)
                         end_pos = end_pos[0], end_pos[1] - 1
                         break
 
-                token_list.append(tok)
+                if tok is not None:  # Can be None, because of lambda/for.
+                    token_list.append(tok)
 
             if not token_list:
                 return None, tok

test/test_parser/test_parser.py

@@ -119,3 +119,9 @@ def test_carriage_return_statements():
     source = source.replace('\n', '\r\n')
     stmt = Parser(source).module.statements[0]
     assert '#' not in stmt.get_code()
+
+
+def test_incomplete_list_comprehension():
+    """ Shouldn't raise an error, same bug as #418. """
+    s = Parser(u('(1 for def')).module.statements[0]
+    assert s.expression_list()