random undefined message causes synckit to throw an error

[dylang]

It looks like we are assuming all recieved messages are objects with a message property: https://github.com/un-ts/synckit/blob/main/src/index.ts#L548

However, sometimes, randomly, only in CI, it seems to receive undefined, which synckit doesn't handle, so it throws an error.

Related: prettier/eslint-plugin-prettier#671

[JounQin]

Without correct reproduction, it's hard to say what is root issue, and are you still having this issue at this time?