fix: 客观题无答案时的显示问题

src/views/base/track-export/useDraw.ts

@@ -811,7 +811,7 @@ export default function useDraw(winId: number) {
           option: {
             x: tagLeft,
             y: tagTop,
-            text: answer,
+            text: answer || '',
             color: isRight ? '#05b575' : '#f53f3f',
           },
         });