Revert "prevent NaN values in .normalizeNormals"

This reverts commit 8d5203fd2f43235c23e0d059b802e207cce69fa8.

src/core/BufferGeometry.js

@@ -818,13 +818,9 @@ THREE.BufferGeometry.prototype = {
 
 			n = 1.0 / Math.sqrt( x * x + y * y + z * z );
 
-			if( isFinite( n ) ) {
-
-				normals[ i ] *= n;
-				normals[ i + 1 ] *= n;
-				normals[ i + 2 ] *= n;
-
-			}
+			normals[ i ] *= n;
+			normals[ i + 1 ] *= n;
+			normals[ i + 2 ] *= n;
 
 		}