Nuxeo harvesting issue: `AttributeError: 'NoneType' object has no attribute 'get'`

[gamontoya]

We're starting to see this issue pop up again when harvesting Nuxeo collections.

AttributeError: 'NoneType' object has no attribute 'get'

Note also the 404 and thumbnail generation errors

• UCM: Fire, Water, Poison, Hope: An Environmental Theater Project

• https://registry.cdlib.org/admin/library_collection/collection/28479

• Dag Run

• Error log: dag_id=harvest_collection_run_id=manual__2025-08-29T17_26_30+00_00_task_id=content_harvesting.content_harvest_map_index=0_attempt=1.log

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Reference: #1190