Currently, the `sqlite3` module does not correctly handle cases where a `Blob` object is accessed after its parent database connection has been closed. **Expected Behavior** To match CPython's behavior, attempting to `read` (or perform other operations) on a blob after calling `connection.close()` should raise a `sqlite3.ProgrammingError` with the message "Cannot operate on a closed database". **Context** This issue prevents the standard library test `test_blob_closed_db_read` from passing. We need to add a check to ensure the connection is still open before processing blob operations.