fix(Playlist): 修复播放次数为 undefined 时的显示问题- 在 Playlist 组件中，为 formatPlayCount 函数调用添加默认值 0

-避免在播放次数为 undefined 或 null 时出现错误或不正确的显示

music-qianduan/src/views/Playlist.vue

@@ -257,7 +257,7 @@ onMounted(() => {
             <div class="playlist-info-overlay">
               <div class="playlist-play-count">
                 <el-icon><video-play /></el-icon>
-                {{ formatPlayCount(playlist.playCount) }}
+                {{ formatPlayCount(playlist.playCount || 0) }}
               </div>
               <div class="playlist-song-count">
                 <el-icon><Headset /></el-icon>
@@ -304,7 +304,7 @@ onMounted(() => {
             <div class="playlist-info-overlay">
               <div class="playlist-play-count">
                 <el-icon><video-play /></el-icon>
-                {{ formatPlayCount(playlist.playCount) }}
+                {{ formatPlayCount(playlist.playCount || 0) }}
               </div>
               <div class="playlist-song-count">
                 <el-icon><Headset /></el-icon>