use faster check

Author: icebob

lib/rules/array.js

@@ -10,7 +10,7 @@ module.exports = function ({ schema, messages }, path, context) {
 		sanitized = true;
 		// Convert to array if not and the value is not null or undefined
 		src.push(`
-			if (!Array.isArray(value) && [null, undefined].indexOf(value) === -1) {
+			if (!Array.isArray(value) && value != null) {
 				value = [value];
 			}
 		`);