fix flickering cuke by inserting "should see"

features/work_packages/index_sums.feature

@@ -67,6 +67,10 @@ Feature: Calculated sums on the work package index
   @javascript
   Scenario: Total sum of summable column should be displayed when display sums checkbox is checked
     When I go to the work packages index page of the project "project1"
+    # Adding this "should see" to prevent the columns menu from being opened
+    # before the information on available columns is returned from the server.
+    # If it is opened before the modal is empty.
+    And I should see "subject" within ".workpackages-table"
     And I choose "Columns" from the toolbar "settings" dropdown
     And I select to see column "Estimated time"
     And I click "Apply"