Attempt to invoke interface method 'int android.database.Cursor.getColumnIndexOrThrow(java.lang.String)' on a null object reference

Question

I am making a music player app and when opening any song from files it comes like this Uri

/external/audio/media/1162591

and when I try to convert this Uri with this code

private String getRealPathFromURI(Uri contentUri) {
    Cursor cursor = null;
    try {
        String[] proj = {MediaStore.Images.Media.DATA};
        cursor = getContentResolver().query(contentUri, proj, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        return cursor.getString(column_index);
    } finally {
        if (cursor != null) {
            cursor.close();
        }
    }
}

It returns error and this is the logcat

2021-06-07 22:58:47.612 6898-6898/com.yapps.ymusic E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.yapps.ymusic, PID: 6898
java.lang.RuntimeException: Failure delivering result ResultInfo{who=@android:requestPermissions:, request=1, result=-1, data=Intent { act=android.content.pm.action.REQUEST_PERMISSIONS (has extras) }} to activity {com.yapps.ymusic/com.yapps.ymusic.MainActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'int android.database.Cursor.getColumnIndexOrThrow(java.lang.String)' on a null object reference
    at android.app.ActivityThread.deliverResults(ActivityThread.java:5041)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:5084)
    at android.app.ActivityThread.-wrap20(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2053)
    at android.os.Handler.dispatchMessage(Handler.java:108)
    at android.os.Looper.loop(Looper.java:166)
    at android.app.ActivityThread.main(ActivityThread.java:7529)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)
 Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'int android.database.Cursor.getColumnIndexOrThrow(java.lang.String)' on a null object reference
    at com.yapps.ymusic.MainActivity.getRealPathFromURI(MainActivity.java:752)
    at com.yapps.ymusic.MainActivity.StringSound(MainActivity.java:740)
    at com.yapps.ymusic.MainActivity.onRequestPermissionsResult(MainActivity.java:677)
    at android.app.Activity.dispatchRequestPermissionsResult(Activity.java:7854)
    at android.app.Activity.dispatchActivityResult(Activity.java:7705)