Return a null duration when there are no playlist entries

src/components/filemanager/Playlists.vue

@@ -189,6 +189,10 @@ export default {
     },
 
     playlistDuration({ item }) {
+      if (!item.entries) {
+        return 0;
+      }
+
       const totalDuration = item.entries.reduce((acc, entry) => {
         const newDuration = acc + entry.duration;