fix:bug修复

ruoyi-ui/src/views/system/bpmnPro/components/Toolbar/tools/Save.vue

@@ -108,7 +108,7 @@ export default {
       const subformData = new FormData();
       // 循环赋值
       for (let key in formData) {
-        subformData.append(key, formData[key]);
+        subformData.append(key, formData[key] == null ? '' : formData[key]);
       }
       if (formData?.processId) {
         updateProcess(subformData).then((res) => {