Use placeholders rather than blank options in bulk issue edit selects.

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

@@ -53,12 +53,16 @@
     - if controller.controller_name == 'issues'
       .issues_bulk_update.hide
         = form_tag bulk_update_namespace_project_issues_path(@project.namespace, @project), method: :post  do
-          = select_tag('update[state_event]', options_for_select([['Open', 'reopen'], ['Closed', 'close']]), prompt: "Status", class: 'form-control')
-          = users_select_tag('update[assignee_id]', placeholder: 'Assignee', null_user: true, first_user: true, current_user: true)
-          = select_tag('update[milestone_id]', bulk_update_milestone_options, prompt: "Milestone")
+          .filter-item.inline
+            = select_tag('update[state_event]', options_for_select([['Open', 'reopen'], ['Closed', 'close']]), include_blank: true, data: { placeholder: "Status" })
+          .filter-item.inline
+            = users_select_tag('update[assignee_id]', placeholder: 'Assignee', null_user: true, first_user: true, current_user: true)
+          .filter-item.inline
+            = select_tag('update[milestone_id]', bulk_update_milestone_options, include_blank: true, data: { placeholder: "Milestone" })
           = hidden_field_tag 'update[issues_ids]', []
           = hidden_field_tag :state_event, params[:state_event]
-          = button_tag "Update issues", class: "btn update_selected_issues btn-save"
+          .filter-item.inline
+            = button_tag "Update issues", class: "btn update_selected_issues btn-save"
 
 :javascript
   new UsersSelect();