Small code style changes

app/views/projects/_readme.html.haml

-- if (readme = @repository.readme) && (readme.rich_viewer)
+- if (readme = @repository.readme) && readme.rich_viewer
   %article.file-holder.readme-holder{ id: 'readme', class: ("limited-width-container" unless fluid_layout) }
     .js-file-title.file-title
       = blob_icon readme.mode, readme.name
       = link_to project_blob_path(@project, tree_join(@ref, readme.path)) do
         %strong
           = readme.name
-    = render 'projects/blob/viewer', viewer: readme.rich_viewer, viewer_url: namespace_project_blob_path(@project.namespace, @project, tree_join(@repository.root_ref, readme.path), viewer: :rich, format: :json)
+    = render 'projects/blob/viewer', viewer: readme.rich_viewer, viewer_url: namespace_project_blob_path(@project.namespace, @project, tree_join(@ref, readme.path), viewer: :rich, format: :json)
 
 - else
   .row-content-block.second-block.center