Switch checking for camera.viewport to camera.isArrayCamera on reflector and refractor

examples/js/objects/Reflector.js

@@ -172,7 +172,7 @@ THREE.Reflector = function ( geometry, options ) {
 
 		// Restore viewport
 
-		if ( camera.viewport !== undefined ) {
+		if ( camera.isArrayCamera ) {
 
 			renderer.state.viewport( camera.viewport );
 

examples/js/objects/Refractor.js

@@ -210,7 +210,7 @@ THREE.Refractor = function ( geometry, options ) {
 
 			// restore viewport
 
-			if ( camera.viewport !== undefined ) {
+			if ( camera.isArrayCamera ) {
 
 				renderer.state.viewport( camera.viewport );