`KeyError: 'fbtrace_id'` when sending event with `ActionSource.APP`

[bdoms]

Everything is working well for us with this SDK, except that we encounter a bug every time we try to set the action source as ActionSource.APP. Changing all the other fields doesn't produce this problem and we can see events coming through correctly.

Given a setup like this:

import os
import uuid

from facebook_business.adobjects.serverside.action_source import ActionSource
from facebook_business.adobjects.serverside.custom_data import CustomData
from facebook_business.adobjects.serverside.event import Event
from facebook_business.adobjects.serverside.event_request_async import EventRequestAsync
from facebook_business.adobjects.serverside.user_data import UserData
from facebook_business.api import FacebookAdsApi

FacebookAdsApi.init(access_token=os.environ['FACEBOOK_ACCESS_TOKEN'])

And then a function that does this:

user_data = UserData(email='user@example.com', phone='+15555550000',
    client_ip_address='127.0.0.1', client_user_agent='a valid user agent')

custom_data = CustomData(currency='usd', value=9.99)

event = Event(
    event_name='Purchase',
    event_time=int(time.time()),
    event_id=f'{event_name}-{uuid.uuid4()}',
    user_data=user_data,
    custom_data=custom_data,
    data_processing_options=[],
    event_source_url='https://www.example.com/checkout',
    action_source=ActionSource.APP
)

event_request_async = EventRequestAsync(events=[event], pixel_id=os.environ['FACEBOOK_PIXEL_ID'])
await event_request_async.execute()

That last lines fails with

File "[redacted]/python3.13/site-packages/facebook_business/adobjects/serverside/event_request_async.py", line 99, in execute
    fbtrace_id=response['fbtrace_id'],
               ~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'fbtrace_id'

Again, it seems like none of the data we're including matters except for the action_source. If it's ActionSource.WEBSITE then this will work correctly without an error every time.

Looking at that line of code here: https://github.com/facebook/facebook-python-business-sdk/blob/main/facebook_business/adobjects/serverside/event_request_async.py#L99

It seems like it's making some assumptions about what's included in the response, when maybe it should be more careful?