CE upstream

CE changes https://gitlab.com/gitlab-org/gitlab-ce/compare/d636efbe26ee51030bb108d889c2ef867570358a...0c36b810abede73b3cf59f951e7467dbac54ec98?expand_all_diffs=1

app/models/repository.rb

@@ -1064,6 +1064,10 @@ def is_ancestor?(ancestor_id, descendant_id)
   end
   def search_files(query, ref)
+    unless exists? && has_visible_content? && query.present?
+      return []
+    end
+
     offset = 2
     args = %W(#{Gitlab.config.git.bin_path} grep -i -I -n --before-context #{offset} --after-context #{offset} -E -e #{Regexp.escape(query)} #{ref || root_ref})
     Gitlab::Popen.popen(args, path_to_repo).first.scrub.split(/^--$/)