allow unset weather provider

aman/sys/WeatherModel.py

@@ -98,6 +98,9 @@ class WeatherModel:
         return ias * math.sqrt(1.225 / self.densityModel(altitude).item())
 
     def updateWindModel(self):
+        if None == self.Weather or None == self.Weather.Provider:
+            return
+
         if None == self.LastWeatherUpdate or self.LastWeatherUpdate != self.Weather.Provider.UpdateTime:
             self.MinimumAltitude = 1000000
             self.MaximumAltitude = -1