Fix: Only allow leaderboard for server songs with numeric IDs

public/src/js/songselect.js

@@ -3335,7 +3335,11 @@ class SongSelect {
 			});
 	}
 	toLeaderboard() {
-		if (!this.songs[this.selectedSong].id) {
+		var songId = this.songs[this.selectedSong].id
+		// Only allow leaderboard for server songs with numeric IDs
+		if (!songId || typeof songId !== 'number' || isNaN(songId)) {
+			// Show alert for custom/local songs
+			alert("排行榜仅支持服务器歌曲\nLeaderboard only available for server songs")
 			return
 		}
 		// Default to first available difficulty if not in a valid difficulty selection
@@ -3347,6 +3351,7 @@ class SongSelect {
 
 		this.clean()
 		this.playSound("se_don")
-		new Leaderboard().display(this.songs[this.selectedSong].id, diffId)
+		new Leaderboard().display(songId, diffId)
 	}
+
 }