Telegram Bot webhook URL gets cleared after couple requests

Question

I created my Telegram Bot and got my token.

I prepared my Bot logic on Firebase Functions with Telegraf.js library.

I set my webhook using setWebhook

When I test my my Telegram Bot, it works fine but after couple requests the Webhook gets cleared.

Here is my Bot's getWebhookInfo:

{
  "ok": true,
  "result": {
    "url": "",
    "has_custom_certificate": false,
    "pending_update_count": 0
  }
}