Notify user, if the coordinates are invalid.

src/extension.js

@@ -880,12 +880,17 @@ const OpenweatherMenuButton = new Lang.Class({
     },
 
     extractCoord: function() {
-        if (!arguments[0])
-            return 0;
+        let coords = 0;
 
-        if (arguments[0].search(">") == -1)
+        if (arguments[0] && (arguments[0].search(">") != -1))
+            coords = arguments[0].split(">")[0];
+
+        if ((coords.search(",") == -1) || isNaN(coords.split(",")[0]) || isNaN(coords.split(",")[1])) {
+            Main.notify("Openweathermap", _("Invalid location, please try to recreate it"));
             return 0;
-        return arguments[0].split(">")[0];
+        }
+
+        return coords;
     },
 
     _onPreferencesActivate: function() {