Alloc default header for empty dbs

[Pavan-Nambi]

closes https://github.com/tursodatabase/turso/issues/3441

turso> select group_concat(name) over () from sqlite_schema;
turso> values (1) intersect values (1);
┌───┐
│ 0 │
├───┤
│ 1 │
└───┘
turso> PRAGMA integrity_check;
┌────┐
│ ok │
└────┘

[penberg]

This pull request has been marked as stale due to inactivity. It will be closed in 7 days if no further activity occurs.

[penberg]

This pull request has been closed due to inactivity. Please feel free to reopen it if you have further updates.