fix: group_by multiple null columns produce phantom row
#9249
| Job | Run time |
|---|---|
| 9s | |
| 2m 5s | |
| 2m 46s | |
| 5m 0s |
group_by multiple null columns produce phantom row
#9249
| Job | Run time |
|---|---|
| 9s | |
| 2m 5s | |
| 2m 46s | |
| 5m 0s |