Method onerror

frontend/src/utils/sse-client.ts:92–94

(handler: ((event: Event) => void) | null)

  }

  set onerror(handler: ((event: Event) => void) | null) {
    this.onerrorHandler = handler;
  }

  get onerror(): ((event: Event) => void) | null {
    return this.onerrorHandler;