Describe the bug
When processing S3 delete events, data-prepper throws a NullPointerException because the object size is null.

To Reproduce

1. Configure an S3 bucket with SQS Event Notifcations and ObjectDelete enabled.
2. Delete a file from the monitored S3 bucket.
3. The following error will occur:
   [s3-source-sqs-1] ERROR org.opensearch.dataprepper.plugins.source.s3.SqsWorker - Unable to process SQS messages. Processing error due to: Cannot invoke "java.lang.Long.longValue()" because the return value of "org.opensearch.dataprepper.plugins.source.s3.S3EventNotification$S3ObjectEntity.getSizeAsLong()" is null

Pipeline config:

  S3-pipeline:
    source:
      s3:
        notification_type: sqs
        codec:
          csv:
        compression: none
        sqs:
          queue_url: "https://sqs.us-east-2.amazonaws.com/someQueue"
        aws:
          region: "us-east-2"
          sts_role_arn: "someArn"

    sink:
      - stdout:

Expected behavior
The application should gracefully handle S3 delete events without throwing an exception. The object size should default to 0 when not present in the event notification.

Proposed Fix

• Add a null check for getSizeAsLong() in the ParsedMessage class.
• Default object size to 0L if the value is null.

Environment (please complete the following information):

• OS: MacOS 14.7 Sonoma
• Data Prepper 2.10.2