modify fdGetter (#19671)

* modify fdGetter

* Check whether a music file is in the OBB file

Author: alexhuangster

cocos/audio/android/AudioEngine-inl.cpp

@@ -97,7 +97,8 @@ static int fdGetter(const std::string& url, off_t* start, off_t* length)
     {
         fd = getObbAssetFileDescriptorJNI(url.c_str(), start, length);
     } 
-    else
+    
+    if (fd <= 0)
     {
         auto asset = AAssetManager_open(cocos2d::FileUtilsAndroid::getAssetManager(), url.c_str(), AASSET_MODE_UNKNOWN);
         // open asset as file descriptor

cocos/platform/android/java/src/org/cocos2dx/lib/Cocos2dxMusic.java

@@ -280,7 +280,7 @@ private MediaPlayer createMediaPlayer(final String path) {
                 mediaPlayer.setDataSource(fis.getFD());
                 fis.close();
             } else {
-                if (Cocos2dxHelper.getObbFile() != null) {
+                if (Cocos2dxHelper.getObbFile() != null && Cocos2dxHelper.getObbFile().getAssetFileDescriptor(path) != null) {
                     final AssetFileDescriptor assetFileDescriptor = Cocos2dxHelper.getObbFile().getAssetFileDescriptor(path);
                     mediaPlayer.setDataSource(assetFileDescriptor.getFileDescriptor(), assetFileDescriptor.getStartOffset(), assetFileDescriptor.getLength());
                 } else {