[messaging] TypeError: Value is not an object: undefined

### [REQUIRED] Step 2: Describe your environment

* Operating System version: MongoDB Atlas Trigger (Realm App)
* Firebase SDK version: 11.4.1
* Firebase Product: messaging
* JS SDK Version: [3.18.0](https://github.com/mongodb/stitch-js-sdk/releases/tag/v3.18.0)
* NPM version: I don't know

### [REQUIRED] Step 3: Describe the problem

Executing `admin.messaging().sendMulticast(message)` returns an error and is not working anymore after upgrading to `firebase-admin: 11.4.1` from `11.0.1` and with the release of [fastify/busboy 1.2.0](https://github.com/firebase/firebase-admin-node/issues/1902#issuecomment-1373978366) :

```
uncaught promise rejection: TypeError: Value is not an object: undefined
```

The difference with my previous issue #1902 is that now `messaging().sendMulticat(message)` is crashing and no longer deliver the push notification.

#### Steps to reproduce:

1. Create a MongoDB Atlas trigger
2. Add `firebase-admin` as external dependency and make sure it's `11.4.1`
3. Add the service-account.json as a `value`
4. Run the code with the below code

#### Relevant Code:

```
exports = async function() {

const admin = require("firebase-admin");
const json_creds = context.values.get("service_account_value_name");

const title = "Test";
const body = "This is a test";

const message= {
android: {
notification: {
title: title,
sound: "default",
body: body,
},
},
apns: {
payload: {
aps: {
alert: {
title: title,
body: body,
},
mutableContent: 1,
contentAvailable: 1
}
},
},
tokens: ["device_token_1", "device_token_2"]
};

admin.initializeApp({
credential: admin.credential.cert(JSON.parse(json_creds))
});

admin.messaging().sendMulticast(message);

console.log("Messages sent !");
}
}
```