Panic when closing rows for a query without columns
When a query has no columns at all (i.e. `""`. or `"-- just a comment"`) the `rows.Close()` method causes a panic.
Example code (and a comparison with to the SQLite driver from mattn)
```go
package main
import (
"database/sql"
"fmt"
_ "github.com/mattn/go-sqlite3"
_ "modernc.org/sqlite"
)
func runQuery(driver string, query string) {
defer func() {
if err := recover(); err != nil {
fmt.Println("!!! panic occurred:", err)
}
}()
fmt.Printf("\nQuery: '%s'\n", query)
db, err := sql.Open(driver, ":memory:")
if err != nil {
fmt.Printf("Error opening the database: %v\n", err)
return
}
defer db.Close()
fmt.Println("Opened the database")
rows, err := db.Query(query)
if err != nil {
fmt.Printf("Error running the query: %v\n", err)
return
}
defer rows.Close()
fmt.Println("Ran the query")
columns, err := rows.Columns()
if err != nil {
fmt.Printf("Error getting columns: %v\n", err)
return
}
if len(columns) == 0 {
fmt.Println("No columns available")
return
}
for rows.Next() {
fmt.Println("Scanning rows")
err := rows.Scan()
if err != nil {
fmt.Printf("Error scanning rows: %v\n", err)
return
}
}
err = rows.Err()
if err != nil {
fmt.Printf("Error with the rows: %v\n", err)
return
}
fmt.Println("Scanned the rows")
}
func main() {
fmt.Println("Starting")
fmt.Println("-- github.com/mattn/go-sqlite3 --")
runQuery("sqlite3", "SELECT 1 WHERE false")
runQuery("sqlite3", "-- just a comment")
runQuery("sqlite3", "")
fmt.Println("-- modernc.org/sqlite --")
runQuery("sqlite", "SELECT 1 WHERE false")
runQuery("sqlite", "-- just a comment")
runQuery("sqlite", "")
fmt.Println("Finished")
}
```
issue