Saving AR results gives TypeError: can only compare to a set

[Lunga001]

Steps to reproduce

Add an AR and submit analyses results
NOTE: This is reproduceable on one of our demo site and I could not reproduce it on my local instance

Current behavior

Saving the results gives this error message
Traceback (innermost last):
Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module bika.lims.browser.analysisrequest.workflow, line 64, in call
Module bika.lims.browser.analysisrequest.workflow, line 342, in workflow_action_submit
Module bika.lims.browser.analyses.workflow, line 219, in workflow_action_submit
Module bika.lims.api, line 655, in search
Module Products.CMFPlone.CatalogTool, line 389, in searchResults
Module Products.ZCatalog.ZCatalog, line 604, in searchResults
Module Products.ZCatalog.Catalog, line 925, in searchResults
Module Products.ZCatalog.Catalog, line 545, in search
Module Products.PluginIndexes.common.UnIndex, line 403, in _apply_index
TypeError: can only compare to a set

Expected behavior

Should save the result and update the AR or Analysis to to_be_verified state

Screenshot (optional)

[Lunga001]

@mikejmets has noted that if we force the affected_ars variable in api/init L218 to be a list like
query = dict(UID=list(affected_ars), portal_type="AnalysisRequest") we don't get the error