Internal Error 500 if I access some project files page on latest version 7.4.3

Not for all projects but some projects.

production log:

1848.Started GET "/beechat/beechat-server/tree/master" for 127.0.0.1 at 2014-10-27 17:51:49 +0800
1849.Processing by Projects::TreeController#show as HTML
1850. Parameters: {"project_id"=>"beechat/beechat-server", "id"=>"master"}
1851.Completed 500 Internal Server Error in 134ms
1852. 
1853.ActionView::Template::Error (undefined method `[]' for nil:NilClass):
1854. 1: - tree, commit = submodule_links(submodule_item)
1855. 2: %tr{ class: "tree-item" }
1856. 3: %td.tree-item-file-name
1857. 4: %i.fa.fa-archive
1858. app/models/repository.rb:162:in `method_missing'
1859. app/models/repository.rb:228:in `submodule_url_for'
1860. app/helpers/submodule_helper.rb:6:in `submodule_links'
1861. app/views/projects/tree/_submodule_item.html.haml:1:in `_app_views_projects_tree__submodule_item_html_haml___2797187596732484734_70366165466680'
1862. app/helpers/tree_helper.rb:19:in `render_tree'
1863. app/views/projects/tree/_tree.html.haml:42:in `_app_views_projects_tree__tree_html_haml__722784179723980777_70366164328860'
1864. app/views/projects/tree/show.html.haml:9:in `_app_views_projects_tree_show_html_haml__2406502409569618592_70366163607600'
1865. app/controllers/projects/tree_controller.rb:13:in `show'