regression: nil values can't be used for arrays

[punkeel]

Passing nil as a value for an Array(T) column used to work, but is broken in master:

To reproduce it locally, I wrote the following script and created a test table.

-- auto-generated definition
create table my_table
(
  id       Int32,
  anything Array(Int8)
)
  engine = Memory;

The following code runs fine with (id) VALUES (?) but breaks with (id, anything) VALUES (?, ?). When the lines annotated with @HERE are uncommented, the script breaks

package main

import (
	"database/sql"
	"fmt"
	_ "github.com/kshvakov/clickhouse"
)

func main() {
	conn, err := sql.Open("clickhouse", "tcp://127.0.0.1:32769")
	if err != nil {
		panic(err)
	}
	fmt.Println("Connected!")

	err = (*conn).Ping()
	if err != nil {
		panic(err)
	}
	fmt.Println("Pinged!") // to force the connection

	tx, err := (*conn).Begin()
	if err != nil {
		panic(err)
	}
	fmt.Println("Got tx!")

	q := "INSERT INTO my_table (id) VALUES (?);"
        // q = "INSERT INTO my_table (id, anything) VALUES (?, ?);" // @HERE
	stmt, err := tx.Prepare(q)
	if err != nil {
		panic(err)
	}
	fmt.Println("Got stmt!")

	stmtParams := make([]interface{}, 0)
	stmtParams = append(stmtParams, sql.NamedArg{Name: "id", Value: 10})
	// stmtParams = append(stmtParams, sql.NamedArg{Name: "anything", Value: nil})  // @HERE

	fmt.Println("Executing!")
	_, err = stmt.Exec(stmtParams...)
	if err != nil {
		panic(err)
	}

	fmt.Println("Done!")
}

Expected behavior: a NULL/default value should be inserted in ClickHouse.
What happens instead:

panic: reflect: call of reflect.Value.Interface on zero Value

goroutine 1 [running]:
reflect.valueInterface(0x0, 0x0, 0x0, 0xc000000001, 0x0, 0x0)
	/usr/local/Cellar/go/1.11.5/libexec/src/reflect/value.go:983 +0x1a0
reflect.Value.Interface(0x0, 0x0, 0x0, 0x12904b0, 0x0)
	/usr/local/Cellar/go/1.11.5/libexec/src/reflect/value.go:978 +0x44
github.com/kshvakov/clickhouse/lib/data.(*Block).AppendRow(0xc0000b2500, 0xc0000aa480, 0x2, 0x2, 0x1400801, 0xc0000aa480)
	/Users/maxime/go/pkg/mod/github.com/kshvakov/clickhouse@v0.0.0-20190401201540-2efe1299a06714f7c1e39b710afcc489c5b7cb01/lib/data/block.go:135 +0x230
github.com/kshvakov/clickhouse.(*stmt).execContext(0xc000090b40, 0x12940e0, 0xc000096008, 0xc0000aa480, 0x2, 0x2, 0x141f8a0, 0x0, 0x0, 0x1705110)
	/Users/maxime/go/pkg/mod/github.com/kshvakov/clickhouse@v0.0.0-20190401201540-2efe1299a06714f7c1e39b710afcc489c5b7cb01/stmt.go:47 +0x67
github.com/kshvakov/clickhouse.(*stmt).ExecContext(0xc000090b40, 0x12940e0, 0xc000096008, 0xc0000ac2d0, 0x2, 0x2, 0xc0000f7cb0, 0xc0000f7cb8, 0x102a1f2, 0xc000000008)
	/Users/maxime/go/pkg/mod/github.com/kshvakov/clickhouse@v0.0.0-20190401201540-2efe1299a06714f7c1e39b710afcc489c5b7cb01/stmt.go:41 +0x144
database/sql.ctxDriverStmtExec(0x12940e0, 0xc000096008, 0x1294320, 0xc000090b40, 0xc0000ac2d0, 0x2, 0x2, 0x2, 0x2, 0x0, ...)
	/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/ctxutil.go:65 +0x216
database/sql.resultFromStatement(0x12940e0, 0xc000096008, 0x1293e20, 0xc0000ee080, 0xc000098200, 0xc0000aa460, 0x2, 0x2, 0x0, 0x0, ...)
	/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:2342 +0x13e
database/sql.(*Stmt).ExecContext(0xc000136000, 0x12940e0, 0xc000096008, 0xc0000aa460, 0x2, 0x2, 0x0, 0x0, 0x0, 0x0)
	/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:2318 +0x1f2
database/sql.(*Stmt).Exec(0xc000136000, 0xc0000aa460, 0x2, 0x2, 0x0, 0x0, 0x1, 0x2)
	/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:2330 +0x65
main.main()
	/Users/maxime/Code/repro_clickhouse/main.go:41 +0x47a