Make sure variable is declared in the scope

https://lgtm.com/projects/g/mrdoob/three.js/snapshot/32fd13b241a1001af0045c3263d17dc2e133f482/files/examples/webgl_geometry_extrude_shapes2.html?sort=name&dir=ASC&mode=heatmap&excluded=false#x827e0a07d6037cbe:1

examples/webgl_geometry_extrude_shapes2.html

@@ -305,7 +305,7 @@
 
 					for ( var j = 0; j < simpleShapes.length; j ++ ) {
 
-						simpleShape = simpleShapes[ j ];
+						var simpleShape = simpleShapes[ j ];
 						var shape3d = new THREE.ExtrudeBufferGeometry( simpleShape, {
 							amount: amount,
 							bevelEnabled: false