fix(wms): 修复库存数量计算潜在空指针异常

- 在计算新的库存数量时，增加了对 changeQty 的空值检查- 避免了在 changeQty 为 null 时可能发生的空指针异常
-确保了库存数量的正确计算和程序的稳定性

ruoyi-modules/hwmom-wms/src/main/java/org/dromara/wms/service/impl/WmsInventoryServiceImpl.java

@@ -422,7 +422,8 @@ public class WmsInventoryServiceImpl implements IWmsInventoryService {
         for (WmsInventoryLedgerVo record : ledgerList) {
             String key = record.getMaterialId() + "_" + record.getBatchCode() + "_" + record.getLocationCode();
             BigDecimal currentBalance = balanceMap.getOrDefault(key, BigDecimal.ZERO);
-            BigDecimal newBalance = currentBalance.add(record.getChangeQty());
+            BigDecimal changeQty = record.getChangeQty() != null ? record.getChangeQty() : BigDecimal.ZERO;
+            BigDecimal newBalance = currentBalance.add(changeQty);
             balanceMap.put(key, newBalance);
             record.setBalanceQty(newBalance);
         }