Get group members only if group not nil

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/controllers/admin/projects_controller.rb

@@ -17,7 +17,10 @@ class Admin::ProjectsController < Admin::ApplicationController
   end
 
   def show
+    if @group
       @group_members = @group.members.order("group_access DESC").page(params[:group_members_page]).per(30)
+    end
+
     @project_members = @project.users_projects.page(params[:project_members_page]).per(30)
   end