diff --git a/src/main/java/com/loafle/overflow/crawler/result/OFResultSetRow.java b/src/main/java/com/loafle/overflow/crawler/result/OFResultSetRow.java
index 557b99c..ac9da46 100644
--- a/src/main/java/com/loafle/overflow/crawler/result/OFResultSetRow.java
+++ b/src/main/java/com/loafle/overflow/crawler/result/OFResultSetRow.java
@@ -89,14 +89,15 @@ public class OFResultSetRow extends OFResultSet{
 
         String metric = metrics.get(findIndex);
 
-        for (int  i =0 ; i< arrayColumns.size() ; ++i) {
-            // replace
-            String k = "$" + i;
-            int dataIndex = this.meta.get(arrayColumns.get(i));
-            String replaceString = data.get(dataIndex);
-            metric = metric.replace(k,"'" + replaceString + "'");
+        if (arrayColumns != null) {
+            for (int  i =0 ; i< arrayColumns.size() ; ++i) {
+                // replace
+                String k = "$" + i;
+                int dataIndex = this.meta.get(arrayColumns.get(i));
+                String replaceString = data.get(dataIndex);
+                metric = metric.replace(k,"'" + replaceString + "'");
+            }
         }
-
         return metric;
     }