Meteor.methods({
    pushSong: function(song) {
        song.owner = this.userId;
        delete song.url;
        return MusicCollection.insert(song);
    }
});

Meteor.methods({
    pushSong: function(song) {
        if(this.userId) {
            song.owner = this.userId;
            delete song.url;
            return MusicCollection.insert(song);
        }
    }
});

Check if user has valid id in method pushSong()
Check if user has valid id in method pushSong()
