Fix GCS operators emitting invalid OpenLineage events with no dataset name

[kacpermuda]

GCSDeleteObjectsOperator and LocalFilesystemToGCSOperator build one OpenLineage Dataset per object/file without checking for falsy values. When objects/src resolves at runtime to a list containing None or "" (e.g. via XCom), or bucket_name/bucket resolves to a falsy value, the emitted event has a Dataset with no name, which violates the OpenLineage spec and gets rejected by consumers, silently dropping lineage for the whole task.

This fixes both operators to skip falsy object/file names and to return an empty OperatorLineage when the bucket is falsy, instead of emitting a malformed event.

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Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Sonnet 5)

Generated-by: Claude Code (Sonnet 5) following the guidelines

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