Submit blank value if nothing selected

If a checkbox is not selected, the browser does not submit it at all.

app/controllers/admin/connected_app_settings_controller.rb

@@ -15,7 +15,7 @@ module Admin
     private
 
     def connected_apps_enabled
-      params.require(:preferences).require(:connected_apps_enabled).join(",")
+      params.require(:preferences).require(:connected_apps_enabled).compact_blank.join(",")
     end
   end
 end

app/views/admin/connected_app_settings/edit.html.haml

@@ -11,6 +11,9 @@
     = t('.info_html')
 
     .field
+      -# Blank value in case nothing is selected
+      = hidden_field_tag("preferences[connected_apps_enabled][]", "")
+
       - ConnectedApp::TYPES.each do |type|
         %label
           = check_box_tag("preferences[connected_apps_enabled][]", type,

spec/system/admin/configuration/connected_app_settings_spec.rb

@@ -22,5 +22,15 @@ RSpec.describe "Connected App Settings", feature: :connected_apps do
     expect{
       click_button "Update"
     }.to change{ Spree::Config.connected_apps_enabled }.to("discover_regen,affiliate_sales_data")
+
+    expect(page).to have_field "Discover Regenerative portal", checked: true
+    expect(page).to have_field "DFC anonymised orders API for research purposes", checked: true
+
+    uncheck "Discover Regenerative portal"
+    uncheck "DFC anonymised orders API for research purposes"
+
+    expect{
+      click_button "Update"
+    }.to change{ Spree::Config.connected_apps_enabled }.to("")
   end
 end