cleanup code

lib/pages/widgets/number_cell.dart

@@ -13,8 +13,7 @@ class NumberCell extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return new Text(
-        this.number == null ? '0' : numberFormatter.format(this.number),
+    return new Text(numberFormatter.format(this.number),
         style: textStyle == null ? theme.textStyle : textStyle);
   }
 }