fix : format null 2 number

@@ -146,6 +146,9 @@ public class SellerOrderViewService {
     }
 
     String buildLeastPriceTips(BigDecimal leastPrice, SkupType skupType){
+        if(leastPrice == null){
+            return null;
+        }
         String prefix = buildLeastPriceTipsPrefix(skupType);
         return prefix==null ? null : prefix + "￥" + BigDecimalHelper.formatNumber(leastPrice, BigDecimalHelper.FORMAT_NOPOINT);
     }