PositionalAudio: Clean up.

src/audio/PositionalAudio.js

@@ -104,11 +104,7 @@ PositionalAudio.prototype = Object.assign( Object.create( Audio.prototype ), {
 
 			Object3D.prototype.updateMatrixWorld.call( this, force );
 
-			if ( ! this.isPlaying ) {
-
-				return;
-
-			}
+			if ( this.isPlaying === false ) return;
 
 			var panner = this.panner;
 			this.matrixWorld.decompose( position, quaternion, scale );