fix(StudyCoursePage): 修复课程详情显示条件逻辑

当课程没有特色、亮点或学习目标时，才显示"暂无详情"。修复了原本逻辑中空状态和详情可能同时显示的问题

@@ -40,7 +40,7 @@
                 </div>
             </div>
 
-            <div id="detail" class="py-4 px-4">
+            <div v-if="course?.feature || course?.highlights || course?.learning_goal" id="detail" class="py-4 px-4">
                 <div v-if="course?.feature">
                     <div class="text-black text-xl font-bold mb-2">课程特色</div>
                     <div class="text-gray-700 text-sm leading-relaxed" v-html="course?.feature"></div>
@@ -56,7 +56,7 @@
                     <div class="text-gray-700 text-sm leading-relaxed" v-html="course?.learning_goal"></div>
                     <br />
                 </div>
-                <van-empty v-else description="暂无详情" />
+                <van-empty v-if="!course?.feature && !course?.highlights && !course?.learning_goal" description="暂无详情" />
             </div>
 
             <div class="h-2 bg-gray-100"></div>