Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which package are you using?

@sentry/serverless

SDK Version

7.11.1

Framework Version

No response

Link to Sentry event

https://sentry.io/organizations/ember/issues/3461754605/events/ef4935183dfb4b5ea54ec171645131b8/?project=6603393

Steps to Reproduce

1. Set up a GCP PubSub function with a handler function that does not have the optional callback argument.

export const rawHandler: EventFunction = async (
  message: PubsubMessage,
  context: CloudEventsContext
): Promise<void> => {

}

2. Wrap your handler function in sentry

export const handler = Sentry.GCPFunction.wrapEventFunction(rawHandler);

3. Run your function

Expected Result

No error is thrown

Actual Result

A TypeError: callback is not a function error is thrown after the handler function has finished executing.

This is the offending line of code https://github.com/getsentry/sentry-javascript/blob/master/packages/serverless/src/gcpfunction/events.ts#L65. It invokes a callback without checking if it exists first.