fix: error handling for quest title

app/src/components/QuestPart.vue

@@ -18,8 +18,12 @@ api
 
 <template>
   <div class="overflow-auto h-full w-full max-h-full">
-    <h1 id="topic" class="text-red-500" v-if="questErr">Failed to get quest infomation</h1>
-    <h1 id="topic" class="text-text" v-else>{{ questData.title }}</h1>
+    <h1 id="topic" class="text-red-500" v-if="questErr">
+      Failed to get quest infomation
+    </h1>
+    <h1 id="topic" class="text-text" v-else-if="questData">
+      {{ questData.title }}
+    </h1>
     <hr class="border-text-line border-2 my-2" />
     <div>
       <p class="text-red-500" v-if="questErr">{{ questErr.message }}</p>