Node-pg-migrate bug silently falls back to PG* env vars

A developer discovered that node-pg-migrate v6.2.2 successfully connected to a database even when the DATABASE_URL was empty, due to an undocumented fallback to PG* environment variables. The package's source code revealed it uses the pg library's default connection logic, which reads PG* vars when no explicit config is provided. This behavior can mask configuration errors and lead to unintended database connections.