fix: Image understanding of non-existent variable prompts

--bug=1050722 --user=刘瑞斌 【应用编排】前置节点删掉后，调试和发布的时候引用前置节点的变量要有提示 https://www.tapd.cn/57709429/s/1635604

ui/src/workflow/nodes/image-understand/index.vue

@@ -221,8 +221,12 @@ const providerOptions = ref<Array<Provider>>([])
 const AIModeParamSettingDialogRef = ref<InstanceType<typeof AIModeParamSettingDialog>>()
 
 const aiChatNodeFormRef = ref<FormInstance>()
+const nodeCascaderRef = ref()
 const validate = () => {
-  return aiChatNodeFormRef.value?.validate().catch((err) => {
+    return Promise.all([
+    nodeCascaderRef.value ? nodeCascaderRef.value.validate() : Promise.resolve(''),
+    aiChatNodeFormRef.value?.validate()
+  ]).catch((err: any) => {
     return Promise.reject({ node: props.nodeModel, errMessage: err })
   })
 }