diff --git a/frontend/src/ts/ervu_business_metrics/formatter/NumberToLocalStringFormatter.ts b/frontend/src/ts/ervu_business_metrics/formatter/NumberToLocalStringFormatter.ts
index 42bf8dd..58bc674 100644
--- a/frontend/src/ts/ervu_business_metrics/formatter/NumberToLocalStringFormatter.ts
+++ b/frontend/src/ts/ervu_business_metrics/formatter/NumberToLocalStringFormatter.ts
@@ -3,6 +3,7 @@ import {FormatterUtils} from "./FormatterUtils";
 
 export class NumberToLocalStringFormatter implements TextFormatter {
   format(value: string): string {
-    return FormatterUtils.toLocalString(value);
+    var result =  FormatterUtils.toLocalString(value);
+    return result ? result : '0';
   }
 }