Search wiki 500 Internal Server Error

Started GET "/search?project_id=16&scope=wiki_blobs&search=ARC" for 127.0.0.1 at 2015-04-30 17:00:33 +0500 Processing by SearchController#show as HTML Parameters: {"project_id"=>"16", "scope"=>"wiki_blobs", "search"=>"ARC"} Completed 500 Internal Server Error in 1130ms

ActionView::Template::Error (undefined method slug' for "documentation.markdown":String): 1: .blob-result 2: .file-holder 3: .file-title 4: = link_to namespace_project_wiki_path(@project.namespace, @project, wiki_blob.filename) do 5: %i.fa.fa-file 6: %strong 7: = wiki_blob.filename app/helpers/wiki_helper.rb:10:in namespace_project_wiki_path' app/views/search/results/_wiki_blob.html.haml:4:in _app_views_search_results__wiki_blob_html_haml__1860964148227322604_84542140' app/views/search/_results.html.haml:24:in _app_views_search__results_html_haml__1896833353871714315_96531700' app/views/search/show.html.haml:22:in block in _app_views_search_show_html_haml__2484843137120806564_101734660' app/views/search/show.html.haml:1:in _app_views_search_show_html_haml__2484843137120806564_101734660'

This problem occurs when the count of search wiki results is greater than 0 only