Fix missing image for last push

app/views/events/_event_last_push.html.haml

 - if show_last_push_widget?(event)
   .event_lp
-    = image_tag "event_push.png"
-     
     %span You pushed to
     = link_to project_commits_path(event.project, event.ref_name) do
       %strong= truncate(event.ref_name, length: 28)