[weather] fixed missing cb crash

modules/weather.js

@@ -66,11 +66,12 @@ function degToDirection(deg) {
 
 module.exports = function (io) {
     var context = {};
+    var firstTime = true;
     var update = function (firstUpdateCb) {
         var then = function () {
-            if (context.current && context.forecast) {
+            if (context.current && context.forecast && firstTime) {
                 firstUpdateCb();
-                then = function () {}
+                firstTime = false;
             }
         };
         fetchCurrent(CITYID, function (current) {