Now with better spelling. Added correct export

src/extras/helpers/PolarGridHelper.js

@@ -92,4 +92,4 @@ function PolarGridHelper( radius, radials, circles, divisions, color1, color2 )
 PolarGridHelper.prototype = Object.create( LineSegments.prototype );
 PolarGridHelper.prototype.constructor = PolarGridHelper;
 
-export { PolarGridHeler };
+export { PolarGridHelper };