tooltip_message is frozen so dup it before sanitizing

It's sad that sanitizing is updating the string directly.

app/views/projects/jobs/_sidebar.html.haml

@@ -86,7 +86,7 @@
       - HasStatus::ORDERED_STATUSES.each do |build_status|
         - builds.select{|build| build.status == build_status}.each do |build|
           .build-job{ class: sidebar_build_class(build, @build), data: { stage: build.stage } }
-            - tooltip = sanitize(build.tooltip_message)
+            - tooltip = sanitize(build.tooltip_message.dup)
             = link_to(project_job_path(@project, build), data: { toggle: 'tooltip', html: 'true', title: tooltip, container: 'body' }) do
               = sprite_icon('arrow-right', size:16, css_class: 'icon-arrow-right')
               %span{ class: "ci-status-icon-#{build.status}" }