[Fix][UI Next][V1.0.0-Alpha] Fix tenant not exists error while import workflow. (#8797)

dolphinscheduler-ui-next/src/views/projects/workflow/components/dag/dag-save-modal.tsx

@@ -148,7 +148,7 @@ export default defineComponent({
       if (process) {
         formValue.value.name = process.name
         formValue.value.description = process.description
-        formValue.value.tenantCode = process.tenantCode
+        formValue.value.tenantCode = process.tenantCode || 'default'
         if (process.timeout && process.timeout > 0) {
           formValue.value.timeoutFlag = true
           formValue.value.timeout = process.timeout