fix

virgo.api/src/main/java/com/bosshand/virgo/api/workark/service/DifyService.java

@@ -177,7 +177,9 @@ public class DifyService {
         df.setElapsedTime(workflowRun.getElapsedTime());
         df.setFinishedAt(workflowRun.getFinishedAt());
         df.setInputs(unicodeEscapeToChinese(workflowRun.getInputs().toString()));
-        df.setOutputs(unicodeEscapeToChinese(workflowRun.getOutputs().toString()));
+        if (workflowRun.getOutputs() != null) {
+            df.setOutputs(unicodeEscapeToChinese(workflowRun.getOutputs().toString()));
+        }
         df.setTotalSteps(workflowRun.getTotalSteps());
         df.setTotalTokens(workflowRun.getTotalTokens());
         difyWorkFlowDao.update(df);