[Bug]: Handle error when prompt is invalid

[dankim444]

What happened?

Right now, the app throws an error when an invalid prompt is provided in an element. There should be a more graceful way of handling this.

What browsers do you see the problem on?

• Firefox
• Chrome
• Safari
• Microsoft Edge

What operating system do you see the problem on?

• Windows
• Mac
• Linux

How did we discover the bug?

• Reported by participant
• Observed on Sentry
• Found in dev

Priority

Blocking all use

[shapeseas]

From @JamesPHoughton: https://github.com/Watts-Lab/deliberation-empirica/blob/f8ea467d2d614845787cc141f849bbc10326aafa/server/src/getTreatments.js#L28