Error: Encoding not recognized: 'undefined'

[White-Bear1122]

When using the MySQL node in Node-RED, which depends on mysql2, to insert data into a table that has triggers after insert and update operations, the charsetNumber property in the connection pool becomes undefined after completing this operation.

Jan 10:25:14 - [red] Uncaught Exception:
Jan 10:25:14 - [error] Error: Encoding not recognized: 'undefined' (searched as: 'undefined')
at Object.getCodec (C:\Users\86157.node-red\node_modules\iconv-lite\lib\index.js:104:23)
at Object.getEncoder (C:\Users\86157.node-red\node_modules\iconv-lite\lib\index.js:115:23)
at exports.encode (C:\Users\86157.node-red\node_modules\mysql2\lib\parsers\string.js:23:25)
at Packet.writeNullTerminatedString (C:\Users\86157.node-red\node_modules\mysql2\lib\packets\packet.js:757:30)
at HandshakeResponse.serializeResponse (C:\Users\86157.node-red\node_modules\mysql2\lib\packets\handshake_response.js:49:12)
at HandshakeResponse.toPacket (C:\Users\86157.node-red\node_modules\mysql2\lib\packets\handshake_response.js:99:20) at ClientHandshake.sendCredentials (C:\Users\86157.node-red\node_modules\mysql2\lib\commands\client_handshake.js:64:46)
at ClientHandshake.handshakeInit (C:\Users\86157.node-red\node_modules\mysql2\lib\commands\client_handshake.js:137:12)
at ClientHandshake.execute (C:\Users\86157.node-red\node_modules\mysql2\lib\commands\command.js:39:22)
at PoolConnection.handlePacket (C:\Users\86157.node-red\node_modules\mysql2\lib\connection.js:425:32)

[CodeSmith32]

@wellwelwel,
Not sure if it's related, but I can reproduce this error with the following:

const pool = mysql.createPool({ /* ... */ });
const conn = await pool.getConnection();

await conn.query("SET NAMES utf8;");
await conn.query("SET NAMES utf8mb4;"); // <-- throws this error

EDIT:

For reference, this can happen if I run code generated by a db export.
Usually these appear at the start, where the script turns off checks:

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET NAMES utf8 */;
/*!50503 SET NAMES utf8mb4 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;