添加对分类列表页不存在二级分类时的逻辑验证

Code Review By Rock Zhang

@@ -64,6 +64,10 @@ class ClassModel
                             'gender' => $genderArr[$k]), 'list')
                     );
 
+                    if(!isset($val['sub'])) {
+                        continue;
+                    }
+                    
                     $subitem = array();
                     foreach ($val['sub'] as $value) {
                         $subitem = array();