Add missing element on page object

I don't know how the has_issue? method was working before without
this element defined, but now it is correctly defined.

qa/qa/page/project/issue/index.rb

@@ -10,6 +10,7 @@ module QA
           end
 
           view 'app/views/projects/issues/_issue.html.haml' do
+            element :issue
             element :issue_link, 'link_to issue.title' # rubocop:disable QA/ElementWithPattern
           end