fix：知识问答回答时空数据替换为 --> 暂无内容

src/pages/Chat/Chat.tsx

@@ -433,12 +433,15 @@ export const Chat: React.FC = () => {
             // 从后往前找到最后一个 AI 项
             for (let i = newItems.length - 1; i >= 0; i--) {
               if (newItems[i].role === 'ai' && newItems[i].answerList?.[0]) {
+                const prevAnswer = newItems[i].answerList[0].answer
                 newItems[i] = {
                   ...newItems[i],
                   answerList: [
                     {
                       ...newItems[i].answerList[0],
                       endAnswerFlag: true,
+                      // 兜底：如果流结束但 answer 仍为空字符串，避免一直显示加载态
+                      answer: prevAnswer === '' ? '暂无内容' : prevAnswer,
                     },
                   ],
                 }
@@ -484,12 +487,14 @@ export const Chat: React.FC = () => {
           // 从后往前找到最后一个 AI 项
           for (let i = newItems.length - 1; i >= 0; i--) {
             if (newItems[i].role === 'ai' && newItems[i].answerList?.[0]) {
+              const prevAnswer = newItems[i].answerList[0].answer
               newItems[i] = {
                 ...newItems[i],
                 answerList: [
                   {
                     ...newItems[i].answerList[0],
                     endAnswerFlag: true,
+                    answer: prevAnswer === '' ? '暂无内容' : prevAnswer,
                   },
                 ],
               }
@@ -516,12 +521,14 @@ export const Chat: React.FC = () => {
           // 从后往前找到最后一个 AI 项
           for (let i = newItems.length - 1; i >= 0; i--) {
             if (newItems[i].role === 'ai' && newItems[i].answerList?.[0]) {
+              const prevAnswer = newItems[i].answerList[0].answer
               newItems[i] = {
                 ...newItems[i],
                 answerList: [
                   {
                     ...newItems[i].answerList[0],
                     endAnswerFlag: true,
+                    answer: prevAnswer === '' ? '暂无内容' : prevAnswer,
                   },
                 ],
               }