missing checking on rows.Err()

https://github.com/uptrace/bun/blob/master/model_map.go
https://github.com/uptrace/bun/blob/master/model_scan.go

According to the https://go.dev/doc/tutorial/database-access
We should add 
```
if err := rows.Err(); err != nil {
}
```

But it is missing in these 2 files