navigator initialize all mission items safely

src/modules/navigator/mission_block.cpp

@@ -59,6 +59,14 @@ using matrix::wrap_pi;
 MissionBlock::MissionBlock(Navigator *navigator) :
 	NavigatorMode(navigator)
 {
+	_mission_item.lat = (double)NAN;
+	_mission_item.lon = (double)NAN;
+	_mission_item.yaw = NAN;
+	_mission_item.loiter_radius = _navigator->get_loiter_radius();
+	_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
+	_mission_item.time_inside = 0.0f;
+	_mission_item.autocontinue = true;
+	_mission_item.origin = ORIGIN_ONBOARD;
 }
 
 bool