增加空值处理

src/main/scala/com/aliyun/odps/spark/examples/makedata_ad/v20240718/diff_data_20240718.scala

@@ -43,7 +43,7 @@ object diff_data_20240718 {
     for (i <- 0 until columns.size()) {
       val column = columns.get(i)
       val name = column.getName
-      val value = record.get(name).toString
+      val value = Option(record.get(name)).map(_.toString).getOrElse("")
       map += (name -> value)
     }
     map