weather: Track whether a location was set

Setting GWeatherInfo:location to null helpfully doesn't mean
"no location", but "NYC". This obviously isn't what we want
to show users, so track the location validity separately and
consider it when updating the label shown to users.

https://bugzilla.gnome.org/show_bug.cgi?id=780252

js/misc/weather.js

@@ -17,6 +17,7 @@ const WeatherClient = new Lang.Class({
 
     _init: function() {
         this._loading = false;
+        this._locationValid = false;
         this._lastUpdate = GLib.DateTime.new_from_unix_local(0);
 
         this._useAutoLocation = false;
@@ -55,6 +56,10 @@ const WeatherClient = new Lang.Class({
         return this._loading;
     },
 
+    get hasLocation() {
+        return this._locationValid;
+    },
+
     get info() {
         return this._weatherInfo;
     },
@@ -64,6 +69,9 @@ const WeatherClient = new Lang.Class({
     },
 
     update: function() {
+        if (!this._locationValid)
+            return;
+
         let now = GLib.DateTime.new_now_local();
         // Update without loading indication if the current info is recent enough
         if (this._weatherInfo.is_valid() &&
@@ -101,6 +109,7 @@ const WeatherClient = new Lang.Class({
 
         this._weatherInfo.abort();
         this._weatherInfo.set_location(location);
+        this._locationValid = (location != null);
 
         if (location)
             this._loadInfo();

js/ui/dateMenu.js

@@ -296,6 +296,9 @@ const WeatherSection = new Lang.Class({
     },
 
     _getLabelText: function() {
+        if (!this._weatherClient.hasLocation)
+            return _("Select a location…");
+
         if (this._weatherClient.loading)
             return _("Loading…");