bug(developer): `TypeError: this.keyboardRequisitioner is undefined`

Sentry Issue: [KEYMAN-DEVELOPER-1X8](https://keyman.sentry.io/issues/5281382462/?referrer=github_integration)

```
TypeError: this.keyboardRequisitioner is undefined
  at KeymanEngine.getKeyboards (@keymanapp/keyman/web/src/app/browser/src/keymanEngine.ts:475:19)
  at buildKeyboardList (/test.js:175:26)
  at window.onload (/test.js:203:3)
```