feat(REQ-3300) - 调整金额变更的处理逻辑

visa/visa-server/src/main/java/cn/axzo/nanopart/visa/server/service/VisaHelper.java

@@ -232,6 +232,9 @@ public class VisaHelper {
     }
 
     public static String buildChangeAmount(BigDecimal changeAmount) {
+        if (Objects.isNull(changeAmount)) {
+            return "";
+        }
         String amountDesc = "不变";
         if (changeAmount.compareTo(BigDecimal.ZERO) > 0) {
             amountDesc = "增加" + changeAmount.abs().toPlainString() + "元";