added error handling to urn upload and spec

Author: reemi1510

app/controllers/admin/urn_lists_controller.rb

@@ -18,7 +18,8 @@ def create
       return redirect_to admin_urn_lists_path
     end
 
-    render action: :new
+  rescue ActionController::ParameterMissing
+    redirect_to new_admin_urn_list_path, alert: 'Please choose a file to upload'
   end
 
   def download

spec/features/admin_can_upload_urn_list_spec.rb

@@ -24,4 +24,14 @@
 
     expect(UrnListImporterJob).to have_been_enqueued
   end
+
+  context 'without attaching a file' do
+    scenario 'displays an error' do
+      visit new_admin_urn_list_path
+
+      click_button 'Upload'
+
+      expect(page).to have_text 'Please choose a file to upload'
+    end
+  end
 end