SDL_mixer: mp3utils.c: Fixed the length with an extended header

SDL Commits
#1 
From 07fb14002a6c77e7d763f6bf612fd1de03d986c5 Mon Sep 17 00:00:00 2001
From: Wohlstand <[EMAIL REDACTED]>
Date: Wed, 21 Dec 2022 12:00:36 +0300
Subject: [PATCH] mp3utils.c: Fixed the length with an extended header

#476
---
 src/codecs/mp3utils.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/codecs/mp3utils.c b/src/codecs/mp3utils.c
index 830e96c4..54bf9af2 100644
--- a/src/codecs/mp3utils.c
+++ b/src/codecs/mp3utils.c
@@ -491,8 +491,8 @@ static SDL_bool parse_id3v2(Mix_MusicMetaTags *out_tags, struct mp3file_t *src)
     }
 
     if (tag_extended_len) {
-        total_length += tag_extended_len + 4;
-        MP3_RWseek(src, tag_extended_len + 4, RW_SEEK_CUR); /* Skip extended header and it's size value */
+        tag_len -= tag_extended_len; /* Subtract the size of extended header */
+        MP3_RWseek(src, tag_extended_len, RW_SEEK_CUR); /* Skip extended header and it's size value */
     }
 
     total_length += tag_len;