FlightTasks: Introduce the empty setpoint to reset the setpoint for every loop iteration and return it in case of no task running

src/lib/FlightTasks/FlightTasks.cpp

@@ -15,6 +15,16 @@ bool FlightTasks::update()
 	return false;
 }
 
+const vehicle_local_position_setpoint_s &FlightTasks::getPositionSetpoint()
+{
+	if (isAnyTaskActive()) {
+		return _current_task->getPositionSetpoint();
+
+	} else {
+		return FlightTask::empty_setpoint;
+	}
+}
+
 int FlightTasks::switchTask(int task_number)
 {
 	/* switch to the running task, nothing to do */