refactor: throw if no 'platforms'

Author: sis0k0

lib/before-watchPatterns.js

@@ -11,7 +11,7 @@ module.exports = function (hookArgs) {
     const { env } = liveSyncData;
     return (args, originalMethod) => {
         return originalMethod(...args).then(originalPatterns => {
-            if (!platforms.length) {
+            if (!platforms || !platforms.length) {
                 throw new Error("Target platform should be specified!");
             }