Fix 'null' to null bug

app/controllers/projects/static_site_editor_controller.rb

@@ -47,6 +47,8 @@ class Projects::StaticSiteEditorController < Projects::ApplicationController
     payload.transform_values do |value|
       if value.is_a?(String) || value.is_a?(Integer)
         value
+      elsif value.nil?
+        ''
       else
         value.to_json
       end

spec/controllers/projects/static_site_editor_controller_spec.rb

@@ -105,7 +105,8 @@ RSpec.describe Projects::StaticSiteEditorController do
                   foo: 'bar'
                 }
               },
-              a_boolean: true
+              a_boolean: true,
+              a_nil: nil
             }
           end
 
@@ -130,6 +131,10 @@ RSpec.describe Projects::StaticSiteEditorController do
           it 'serializes data values which are hashes to JSON' do
             expect(assigns_data[:a_hash]).to eq('{"a_deeper_hash":{"foo":"bar"}}')
           end
+
+          it 'serializes data values which are nil to an empty string' do
+            expect(assigns_data[:a_nil]).to eq('')
+          end
         end
       end
     end