Fix: Validate songId as number and add user notification for leaderboard submission

public/src/js/leaderboard.js

@@ -77,9 +77,16 @@ class Leaderboard {
     }
 
     async fetchLeaderboard() {
+        // Validate songId is a valid number
+        if (!this.songId || isNaN(parseInt(this.songId))) {
+            console.error("Invalid song ID for leaderboard:", this.songId)
+            this.leaderboardData = []
+            return
+        }
+
         try {
             var response = await loader.ajax(
-                `${gameConfig.basedir || "/"}api/leaderboard/get?song_id=${this.songId}&difficulty=${this.difficulty}`
+                `${gameConfig.basedir || "/"}api/leaderboard/get?song_id=${parseInt(this.songId)}&difficulty=${this.difficulty}`
             )
             var data = JSON.parse(response)
             if (data.status === "ok") {
@@ -94,6 +101,7 @@ class Leaderboard {
         }
     }
 
+
     changeDifficulty(direction) {
         var difficulties = ["easy", "normal", "hard", "oni", "ura"]
         var currentIndex = difficulties.indexOf(this.difficulty)