fix link on project member overview box

app/views/projects/_members_box.html.erb

@@ -38,8 +38,8 @@ See doc/COPYRIGHT.rdoc for more details.
         <%= role %>: <%= users.sort.collect{ |u| link_to_user u }.join(", ").html_safe %><br />
       <% end %>
     </p>
-    <% if current_user.admin? %>
-      <%= link_to new_user_path, class: 'button -alt-highlight' do %>
+    <% if current_user.allowed_to?(:manage_members, @project) %>
+      <%= link_to project_members_path(project_id: @project.identifier), class: 'button -alt-highlight' do %>
         <i class="button--icon icon-add"></i>
         <span class="button--text"><%= l('activerecord.models.member') %></span>
       <% end %>