NoMethodError in MaterialsController#index

undefined method `excluded?' for #<String:0x00007fedbca2b690> Did you mean? exclude?

Extracted source (around line #24):
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respond_to do |format|
format.json { render json: @results_and_paginated }
format.json_api { render json: @results_and_paginated }
format.html
end

Rails.root: /opt/training-catalogue

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"author"=>"[\"Abigail\", \"McBirnie\"]", "target_audience"=>"librarians"}

Response

Headers:

None