[Fix] Fixed some bugs

[Doushabo]

MelonLoader: v0.7.3
Mod Version: v2.1.0
Game Version: v6.6.0

1. Fixed the issue of Transform child out of bounds

Latest.log: Latest.log

Bug reproduction: After clicking the sound settings page, the console will output an error message.

[18:22:47.416] [ERROR] [Il2CppInterop] During invoking native->managed trampoline
Il2CppInterop.Runtime.Il2CppException: UnityEngine.UnityException: Transform child out of bounds
--- BEGIN IL2CPP STACK TRACE ---
UnityEngine.UnityException: Transform child out of bounds

--- END IL2CPP STACK TRACE ---

   at Il2CppInterop.Runtime.Il2CppException.RaiseExceptionIfNecessary(IntPtr returnedException) in /home/runner/work/Il2CppInterop/Il2CppInterop/Il2CppInterop.Runtime/Il2CppException.cs:line 36
   at UnityEngine.Transform.GetChild(Int32 index)
   at CustomHitSound.Extensions.<>c.<GetChild>b__0_0(Transform current, Int32 index)
   at System.Linq.Enumerable.Aggregate[TSource,TAccumulate](IEnumerable`1 source, TAccumulate seed, Func`3 func)
   at CustomHitSound.Extensions.GetChild(Transform transform, Int32[] indexes)
   at CustomHitSound.Patches.VolumeSelectPatch.Postfix(VolumeSelect __instance)
   at DMD<Il2Cpp.VolumeSelect::SetSelectImage>(VolumeSelect this, GameObject currentObj)
   at (il2cpp -> managed) SetSelectImage(IntPtr , IntPtr , Il2CppMethodInfo* )

The reason is that the game update caused this issue, so specific adjustments were made accordingly.

2. Fixed the issue where the sound effect package lacked the 'sfx_press_horse' file, which was instead replaced by Hoofbeat.

3. The Mod version number has been updated to 2.1.2.