fix(instructeurs): don't fail when removing all displayed fields

app/controllers/instructeurs/procedures_controller.rb

@@ -134,7 +134,8 @@ module Instructeurs
     end
 
     def update_displayed_fields
-      values = params['values'].presence || []
+      values = (params['values'].presence || []).reject(&:empty?)
+
       procedure_presentation.update_displayed_fields(values)
 
       redirect_back(fallback_location: instructeur_procedure_url(procedure))

spec/system/instructeurs/procedure_filters_spec.rb

@@ -60,6 +60,12 @@ describe "procedure filters" do
       expect(page).not_to have_link(type_de_champ.libelle)
       expect(page).not_to have_link(champ.value)
     end
+
+    # Test removal of all customizable fields
+    remove_column("Demandeur")
+    within ".dossiers-table" do
+      expect(page).not_to have_link("Demandeur")
+    end
   end
 
   scenario "should be able to add and remove filter", js: true do