fixed npe bug.

Author: m4gr3d

ServiceApp/src/org/droidplanner/services/android/core/drone/DroneManager.java

@@ -60,6 +60,7 @@
 import org.droidplanner.services.android.core.drone.autopilot.px4.Px4Native;
 import org.droidplanner.services.android.core.drone.companion.solo.SoloComp;
 import org.droidplanner.services.android.core.drone.variables.HeartBeat;
+import org.droidplanner.services.android.core.drone.variables.StreamRates;
 import org.droidplanner.services.android.core.drone.variables.calibration.MagnetometerCalibrationImpl;
 import org.droidplanner.services.android.core.firmware.FirmwareType;
 import org.droidplanner.services.android.core.gcs.GCSHeartbeat;
@@ -77,6 +78,8 @@
 import org.droidplanner.services.android.utils.analytics.GAUtils;
 import org.droidplanner.services.android.utils.prefs.DroidPlannerPrefs;
 
+import org.droidplanner.services.android.core.drone.profiles.Parameters;
+
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
@@ -280,15 +283,26 @@ public void postDelayed(Runnable thread, long timeout) {
                 break;
         }
 
-        this.drone.getStreamRates().setRates(dpPrefs.getRates());
-
         this.followMe = new Follow(this, handler, new FusedLocation(context, handler));
         this.returnToMe = new ReturnToMe(this, new FusedLocation(context, handler,
                 LocationRequest.PRIORITY_HIGH_ACCURACY, 1000L, 1000L, ReturnToMe.UPDATE_MINIMAL_DISPLACEMENT), this);
 
+        final StreamRates streamRates = drone.getStreamRates();
+        if(streamRates != null) {
+            streamRates.setRates(dpPrefs.getRates());
+        }
+
         drone.addDroneListener(this);
-        drone.getParameters().setParameterListener(this);
-        drone.getMagnetometerCalibration().setListener(this);
+
+        final Parameters parameters = drone.getParameters();
+        if(parameters != null) {
+            parameters.setParameterListener(this);
+        }
+
+        final MagnetometerCalibrationImpl magnetometer = drone.getMagnetometerCalibration();
+        if(magnetometer != null) {
+            magnetometer.setListener(this);
+        }
     }
 
     public SoloComp getSoloComp() {