[princejain756]

Fixes #3826

When a PostgreSQL backend sends an ErrorResponse with severity set to 'FATAL' or 'PANIC' while an active query is running, the server closes the session immediately without sending ReadyForQuery. Previously, _handleErrorWhileQuerying routed the error to activeQuery.handleError without updating this._queryable, leaving client._queryable === true between the error callback firing and the TCP socket closing.

Any query issued inside the FATAL error callback was written onto a connection the server had already terminated, or allowed a pooled client to look reusable before end arrived.

This sets this._queryable = false in _handleErrorWhileQuerying when msg.severity === 'FATAL' || msg.severity === 'PANIC', while leaving normal 'ERROR' responses untouched.