[bugfix] fix null point for empty list

atms-api/src/main/java/pwc/taxtech/atms/vat/service/impl/OutputInvoiceServiceImpl.java

@@ -86,15 +86,20 @@ public class OutputInvoiceServiceImpl extends VatAbstractService {
     }
 
     public OperationResultDto<List<OutputVATInvoiceInfoDto>> getOutputInvoiceList(Integer period) {
-        List<OutputVATInvoiceInfoDto> result = outputVATInvoiceMapper.queryOutputDetailWithItem(period);
-        result.sort(Comparator.comparing(OutputVATInvoiceInfoDto::getInvoiceID));
+        List<OutputVATInvoiceInfoDto> result = new ArrayList<>();
         OperationResultDto<List<OutputVATInvoiceInfoDto>> dtoResult = new OperationResultDto();
 
-        OutputVATInvoiceExample example = new OutputVATInvoiceExample();
-        example.createCriteria().andPeriodIDEqualTo(period.intValue());
+        result.addAll(outputVATInvoiceMapper.queryOutputDetailWithItem(period));
+        if (!result.isEmpty()) {
+            result.sort(Comparator.comparing(OutputVATInvoiceInfoDto::getInvoiceID));
+            OutputVATInvoiceExample example = new OutputVATInvoiceExample();
+            example.createCriteria().andPeriodIDEqualTo(period.intValue());
+            dtoResult.setReturnCode(Long.valueOf(outputVATInvoiceMapper.countByExample(example)).intValue());
+        }else {
+            dtoResult.setReturnCode(0);
+        }
 
         dtoResult.setData(result);
-        dtoResult.setReturnCode(Long.valueOf(outputVATInvoiceMapper.countByExample(example)).intValue());
         dtoResult.setResult(true);
         return dtoResult;
     }