Fix md_preview

app/views/projects/_md_preview.html.haml

 - referenced_users = local_assigns.fetch(:referenced_users, nil)
 
 - if defined?(@merge_request) && @merge_request.discussion_locked?
-.issuable-note-warning
-  = icon('lock')
-  %span
-    = _('This merge request is locked.')
-    = _('Only project members can comment.')
+  .issuable-note-warning
+    = icon('lock')
+    %span
+      = _('This merge request is locked.')
+      = _('Only project members can comment.')
 
 .md-area
   .md-header