NoMethodError: undefined method `attributes' for nil:NilClass

[lpirola]

https://sentry.io/nossas-cidades/bonde-server/issues/436571061/

NoMethodError: undefined method `attributes' for nil:NilClass
  app/controllers/mobilizations/form_entries_controller.rb:57:in `block in to_csv'
    csv << fst.attributes.keys
  app/controllers/mobilizations/form_entries_controller.rb:56:in `to_csv'
    CSV.generate(headers: true) do |csv|
  app/controllers/mobilizations/form_entries_controller.rb:29:in `block (2 levels) in index'
    send_data to_csv(@form_entries), type: Mime::CSV, disposition: "attachment; filename=form_entries_#{DateTime.now.to_i}_#{parent.community.name.parameterize}_#{parent.id}.csv"
  app/controllers/mobilizations/form_entries_controller.rb:24:in `index'
    respond_with do |format|
...
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NoMethodError: undefined method `attributes' for nil:NilClass