'.action_context' should be string

{"action_context":null,"element_friendly_name":"Device back button","experiment":{"enrolled":"growthexperiments-editattempt-anonwarning","assigned":"control","subject_id":"tqgJKUIaTF9qaKEaxPWyuw","sampling_unit":"edge-unique","coordinator":"default","other_assigned":{"we-1-10-articleguidance-v1":"control"}},"$schema":"/analytics/product_metrics/web/base/2.0.0","meta":{"domain":"es.wikipedia.org","stream":"mediawiki.product_metrics.contributors.experiments","id":"a9ff5a20-c7fa-4676-815d-558942528f3d","dt":"2026-05-06T23:37:39.102Z","request_id":"aceedc9c-4703-4465-a873-b3d338fe5f40"},"dt":"2026-05-06T23:37:37.681Z","action":"navigation_back","agent":{"client_platform":"mediawiki_js","client_platform_family":"mobile_browser"},"performer":{"is_logged_in":true,"is_temp":false,"is_bot":false,"id":6155760,"edit_count":80119},"mediawiki":{"skin":"minerva","database":"eswiki"}}