Update builds.

build/three.js

@@ -9538,7 +9538,7 @@
 
 			var face = {
 				a: a,
-				b: a,
+				b: b,
 				c: c,
 				normal: new Vector3(),
 				materialIndex: 0

build/three.module.js

@@ -11067,7 +11067,7 @@ function checkBufferGeometryIntersection( object, material, raycaster, ray, posi
 
 		const face = {
 			a: a,
-			b: a,
+			b: b,
 			c: c,
 			normal: new Vector3(),
 			materialIndex: 0