weather probe not working when air quality is included

Weather seems to work ok when I use all sensors excluding air quality. Once I add air quality I don't get anything anymore from weather.

code (with sampling every 10s. In real experiment the sampling will obviously be at a lower frequency).

```
AirQualityService airService =
AirQualityService(apiKey: APIAIR);
protocol.addConnectedDevice(airService);

protocol.addTriggeredTask(
IntervalTrigger(period: Duration(seconds: 10)),
BackgroundTask()
..addMeasure(Measure(type: ContextSamplingPackage.AIR_QUALITY)),
airService);

WeatherService weatherService =
WeatherService(apiKey: APIWEATHER);
protocol.addConnectedDevice(weatherService);

protocol.addTriggeredTask(
IntervalTrigger(period: Duration(seconds: 10)),
BackgroundTask()
..addMeasure(Measure(type: ContextSamplingPackage.WEATHER)),
weatherService);
```