Firebase function onWrite-Trigger returns null event.data when key/push-id ends in numbers

[Merve40]

The event Argument in Firebase Function-Trigger for onWrite(event) returns null, if the key/push-id ends in numbers.

exports.notify = functions.database.ref("/Message/{pushId}").onWrite(event => {
    const body = event.data.val(); // returns null
    ...
}

Version info

firebase-tools: 3.14.0
firebase-functions:^0.7.1

Test case & How to reproduce

https://my-firebase-url.com/Message/{pushId}/..

This push-id cannot be recognized by the trigger, thus returns null as argument:
https://my-firebase-url.com/Message/n_12/..

This push-id works:
https://my-firebase-url.com/Message/blabla/..

[inlined]

Tried very hard to reproduce this but I can't. I strongly suspect you're getting a null because the onWrite event also fires when the pushId is deleted (where the value is correctly "null"). If you only want to handle creation events, you can listen to onCreate instead.