`this.fastboot` is possibly `undefined`

[nathanhammond]

In the event of a notification that triggers reload, this.fastboot is possibly undefined:

fastboot-app-server/src/worker.js

Line 62 in a5d194e

this.fastboot.reload();

this.fastboot comes into existence conditionally based upon:

fastboot-app-server/src/worker.js

Lines 45 to 49 in a5d194e

	if (!this.distPath) {
	this.middleware = this.noAppMiddleware();
	} else {
	this.middleware = this.buildMiddleware();
	}