Merge branch 'bugfix/153/500_when_create_issue' into 'master'

Fix 500 Error When Creating Issue For Project With No Commits

This merge request fixes issue #153, where trying to create an issue for a project with no commits results in a 500 error. This was done by updating the form to check that the repository wasn't empty before trying to load the contribution guide.

app/views/projects/issues/_form.html.haml

 %div.issue-form-holder
   %h3.page-title= @issue.new_record? ? "New Issue" : "Edit Issue ##{@issue.iid}"
   %hr
-  - if @repository.contribution_guide && !@issue.persisted?
+  - if !@repository.empty? && @repository.contribution_guide && !@issue.persisted?
     - contribution_guide_url = project_blob_path(@project, tree_join(@repository.root_ref, @repository.contribution_guide.name))
     .alert.alert-info.col-sm-10.col-sm-offset-2
       ="Please review the <strong>#{link_to "guidelines for contribution", contribution_guide_url}</strong> to this repository.".html_safe