fix null

src/main/scala/com/gmei/data/dq/pvCheker.scala

@@ -40,7 +40,8 @@ object pvCheker {
     */
     val df = sc.sql(s"""
       select
-        cl_id, action, cl_type, app_version, params['page_name'] as page_name,
+        cl_id, action, cl_type, app_version,
+        case when params['page_name'] is null then 'NULL' else params['page_name'],
         case when params['extra_param'] is null then 0 else 1 end as extra,
         case
           when params['referrer'] is null then -1