Meet `invalid memory address or nil pointer dereference`

[zeminzhou]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. start up TiDB cluseter by tiup
2. import data
3. exeute the flowing sql:

USE sample_data;
WITH starts_by_day AS
  (SELECT repo_name,
          date(created_at) AS DAY,
          COUNT(1) AS stars
   FROM github_events
   WHERE TYPE = 'WatchEvent'
   GROUP BY repo_name,
            DAY)
SELECT s.repo_name,
       max(s.stars) AS daily_stars,
       sum(s.stars) AS total_stars,
       sum(s.stars) / max(s.stars) AS rate
FROM starts_by_day AS s
GROUP BY repo_name
ORDER BY rate DESC
LIMIT 10;

2. What did you expect to see? (Required)

sql executed successfully

3. What did you see instead (Required)

runtime error: invalid memory address or nil pointer dereference

4. What is your TiDB version? (Required)

nightly