handle badly-formatted previous search UUIDs

[longhotsummer]

fixes https://lawsafrica.sentry.io/issues/5388006767/

[sentry-io[bot]]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ RequestError: RequestError(400, 'search_phase_execution_exception', '[inner_hits] already contains an entry for... /search/api/documents/ View Issue

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