[BUG] Empty DLQ entries when version conflicts occur

[engechas]

Describe the bug
An empty DLQ object is created when there are failures shipping to OpenSearch but all of the failures are due to a version conflict. The code here filters out version conflicts from the DLQ entries: https://github.com/opensearch-project/data-prepper/blob/main/data-prepper-plugins/opensearch/src/main/java/org/opensearch/dataprepper/plugins/sink/opensearch/BulkRetryStrategy.java#L353-L356

But then there is no empty check before sending the doc list to the DLQ: https://github.com/opensearch-project/data-prepper/blob/main/data-prepper-plugins/opensearch/src/main/java/org/opensearch/dataprepper/plugins/sink/opensearch/BulkRetryStrategy.java#L369

To Reproduce
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4. See error

Expected behavior
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Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04 LTS]
• Version [e.g. 22]

Additional context
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[amitkirdatt]

Told by AWS Support that this issue is related to the issue that I opened here: #4304