panicked when using window function

[winoros]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

CREATE TABLE t1(i INT, j INT, k INT);
INSERT INTO t1 VALUES (1,1,1),(2,2,2),(3,3,3),(4,4,4);
INSERT INTO t1 SELECT 10*i,j,5*j FROM t1 UNION SELECT 20*i,j,5*j FROM t1
UNION SELECT 30*i,j,5*j FROM t1;

SELECT SUM(i) OVER W FROM t1 WINDOW w AS (PARTITION BY j ORDER BY i)
  ORDER BY 1+SUM(i) OVER w;

2. What did you expect to see?

Execute successfully

3. What did you see instead?

Panicked

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

master 373317f