Ignore harmless errors (un)subscribing to the message bus.

app/src/main/java/info/nightscout/androidaps/MainApp.java

@@ -245,12 +245,27 @@ public class MainApp extends Application {
         }
     }
 
-
     public void stopKeepAliveService() {
         if (keepAliveReceiver != null)
             KeepAliveReceiver.cancelAlarm(this);
     }
 
+    public static void subscribe(Object subscriber) {
+        try {
+            bus().register(subscriber);
+        } catch (IllegalArgumentException e) {
+            // already registered
+        }
+    }
+
+    public static void unsubscribe(Object subscriber) {
+        try {
+            bus().unregister(subscriber);
+        } catch (IllegalArgumentException e) {
+            // already unregistered
+        }
+    }
+
     public static Bus bus() {
         return sBus;
     }

app/src/main/java/info/nightscout/androidaps/plugins/Overview/Dialogs/BolusProgressDialog.java

@@ -75,7 +75,7 @@ public class BolusProgressDialog extends DialogFragment implements View.OnClickL
         } else {
             if (getDialog() != null)
                 getDialog().getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
-            MainApp.bus().register(this);
+            MainApp.subscribe(this);
             running = true;
         }
     }
@@ -97,7 +97,7 @@ public class BolusProgressDialog extends DialogFragment implements View.OnClickL
     @Override
     public void onPause() {
         super.onPause();
-        MainApp.bus().unregister(this);
+        MainApp.unsubscribe(this);
         running = false;
     }