Set default value for show_menu_above variable.

app/views/shared/issuable/_milestone_dropdown.html.haml

 - project = @target_project || @project
 - extra_class = extra_class || ''
+- show_menu_above = show_menu_above || false
 - selected_text = selected.try(:title)
 - if selected.present?
   = hidden_field_tag(name, name == :milestone_title ? selected.title : selected.id)
 = dropdown_tag(milestone_dropdown_label(selected_text), options: { title: "Filter by milestone", toggle_class: "js-milestone-select js-filter-submit #{extra_class}", filter: true, dropdown_class: "dropdown-menu-selectable dropdown-menu-milestone",
-  placeholder: "Search milestones", footer_content: project.present?, data: { show_no: true, show_menu_above: true, show_any: show_any, show_upcoming: show_upcoming, field_name: name, selected: selected.try(:title), project_id: project.try(:id), milestones: milestones_filter_dropdown_path, default_label: "Milestone" } }) do
+  placeholder: "Search milestones", footer_content: project.present?, data: { show_no: true, show_menu_above: show_menu_above, show_any: show_any, show_upcoming: show_upcoming, field_name: name, selected: selected.try(:title), project_id: project.try(:id), milestones: milestones_filter_dropdown_path, default_label: "Milestone" } }) do
   - if project
     %ul.dropdown-footer-list
       - if can? current_user, :admin_milestone, project