apps-android-commons: App crashes when opening *Nearby* in a particular scenario

Summary: Nearby crashes when the phone is connected to a network that is disconnected from the ISP’s network. To be more detailed, I use a Wi-Fi enabled data modem with the ability to disconnect the data service. So, when I disconnect the data service and connect the phone to the Wi-Fi network (which isn’t connected to the ISP’s network) and visit Nearby, the app crashes.

Steps to reproduce:

1. Connect to a network that isn’t connected to the ISP’s network in some way (one way is described in the summary)
2. Open the app
3. Open Nearby

Add System logs:

D/NearbyPlaces: java.net.ConnectException: failed to connect to query.wikidata.org/192.168.206.84 (port 443): connect failed: ECONNREFUSED (Connection refused)
D/NearbyPlaces: back to initial radius: 1.000000
W/System.err: io.reactivex.exceptions.OnErrorNotImplementedException: Callable returned null
W/System.err:     at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
W/System.err:     at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
W/System.err:     at io.reactivex.internal.observers.LambdaObserver.onError(LambdaObserver.java:74)
W/System.err:     at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.checkTerminated(ObservableObserveOn.java:276)
W/System.err:     at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.drainNormal(ObservableObserveOn.java:172)
W/System.err:     at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.run(ObservableObserveOn.java:252)
W/System.err:     at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:109)
W/System.err:     at android.os.Handler.handleCallback(Handler.java:739)
W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:95)
W/System.err:     at android.os.Looper.loop(Looper.java:145)
W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:6946)
W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
W/System.err:     at java.lang.reflect.Method.invoke(Method.java:372)
W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
W/System.err: Caused by: java.lang.NullPointerException: Callable returned null
W/System.err:     at io.reactivex.internal.functions.ObjectHelper.requireNonNull(ObjectHelper.java:39)
W/System.err:     at io.reactivex.internal.operators.observable.ObservableFromCallable.subscribeActual(ObservableFromCallable.java:42)
W/System.err:     at io.reactivex.Observable.subscribe(Observable.java:10901)
W/System.err:     at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)
W/System.err:     at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452)
W/System.err:     at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:61)
W/System.err:     at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:52)
W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
W/System.err:     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
W/System.err:     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
W/System.err:     at java.lang.Thread.run(Thread.java:818)
E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: fr.free.nrw.commons.debug, PID: 16239
                  io.reactivex.exceptions.OnErrorNotImplementedException: Callable returned null
...
I/Process: Sending signal. PID: 16239 SIG: 9

Expected behavior: Warn about the inability to connect to the network.

Observed behavior: The app crashes.

Device and Android version: Device: Samsung Galaxy J2 Android: 5.1.1

Commons app version: 2.7.1

Would you like to work on the issue? Nope, sorry ☺️