--restore-database-mapping panic

[Slach]

goroutine 1 [running]:
[github.com/AlexAkulov/clickhouse-backup/pkg/backup.(*Backuper).prepareRestoreDatabaseMapping(0xc0000fed90](http://github.com/AlexAkulov/clickhouse-backup/pkg/backup.(*Backuper).prepareRestoreDatabaseMapping(0xc0000fed90), {0xc0008c0350, 0x1, 0x0?})
        /home/runner/work/clickhouse-backup/clickhouse-backup/pkg/backup/restore.go:194 +0x13a
[github.com/AlexAkulov/clickhouse-backup/pkg/backup.(*Backuper).Restore(0xc0000fed90](http://github.com/AlexAkulov/clickhouse-backup/pkg/backup.(*Backuper).Restore(0xc0000fed90), {0x7ffc93105871, 0x5}, {0x7ffc9310585d, 0x13}, {0xc0008c0350, 0x1, 0x1}, {0x22f5ed0, 0x0, ...}, ...)
        /home/runner/work/clickhouse-backup/clickhouse-backup/pkg/backup/restore.go:39 +0x125
main.main.func9(0xc0008c62c0)
        /home/runner/work/clickhouse-backup/clickhouse-backup/cmd/clickhouse-backup/main.go:258 +0x2a9
[github.com/urfave/cli.HandleAction({0x1248760](http://github.com/urfave/cli.HandleAction(%7B0x1248760)?, 0x1525030?}, 0x7?)
        /home/runner/go/pkg/mod/github.com/urfave/cli@v1.22.10/app.go:524 +0x50
[github.com/urfave/cli.Command.Run({{0x14a4d22](http://github.com/urfave/cli.Command.Run(%7B%7B0x14a4d22), 0x7}, {0x0, 0x0}, {0x0, 0x0, 0x0}, {0x14e22ae, 0x2a}, {0x1503747, ...}, ...}, ...)
        /home/runner/go/pkg/mod/github.com/urfave/cli@v1.22.10/command.go:173 +0x65b
[github.com/urfave/cli.(*App).Run(0xc0008b6000](http://github.com/urfave/cli.(*App).Run(0xc0008b6000), {0xc00003e0a0, 0x5, 0x5})
        /home/runner/go/pkg/mod/github.com/urfave/cli@v1.22.10/app.go:277 +0x8c7
main.main()
        /home/runner/work/clickhouse-backup/clickhouse-backup/cmd/clickhouse-backup/main.go:504 +0x3a33