AwsLambdaIntegration crashes when lambda is triggered by EventBridge Pipe source

[davidcroda]

How do you use Sentry?

Sentry Saas (sentry.io)

Version

1.38.0

Steps to Reproduce

1. Create an EventBridge pipe in AWS with any source, and a destination of a lambda function
2. Instrument the lambda function with sentry and include the AwsLambdaIntegration
3. Observe that when triggered by events from the pipe, sentry errors out while trying to trace the function

The following is the stack trace that is printed out in the logs

AttributeError: 'list' object has no attribute 'items'
Traceback (most recent call last):
  File "/var/task/sentry_sdk/integrations/aws_lambda.py", line 145, in sentry_handler
    transaction = continue_trace(
  File "/var/task/sentry_sdk/api.py", line 269, in continue_trace
    return Hub.current.continue_trace(environ_or_headers, op, name, source)
  File "/var/task/sentry_sdk/hub.py", line 596, in continue_trace
    normalize_incoming_data(environ_or_headers),
  File "/var/task/sentry_sdk/tracing_utils.py", line 497, in normalize_incoming_data
    for key, value in incoming_data.items():

Expected Result

Sentry is able to trace the function invocation

Actual Result

Sentry crashes and ends execution of the function.

The root of the issue seems to be that the AwsLambdaIntegration expects that if the headers key exists in the request, that it will be a dictionary. However when EventBridge triggers the lambda with data, it sends headers as an empty list. Sample payload below.

[
{
    "topic": "lps-ranges",
    "partition": 1,
    "offset": 0,
    "timestamp": 1701268939207,
    "timestampType": "CREATE_TIME",
    "key": "REDACTED",
    "value": "REDACTED",
    "headers": [],
    "eventSourceArn": "REDACTED",
    "bootstrapServers": "REDACTED",
    "eventSource": "aws:kafka",
    "eventSourceKey": "lps-ranges-1"
}
]

This is where the error is caused in the lambda integration. https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/integrations/aws_lambda.py#L140-L143

This should probably be inverted to set headers to an empty dict if it is not a dict, instead of checking only if it is None.