AC_WPNav: remove pointless initialisations

new clears this memory

libraries/AC_WPNav/AC_WPNav.cpp

@@ -78,21 +78,7 @@ AC_WPNav::AC_WPNav(const AP_InertialNav& inav, const AP_AHRS_View& ahrs, AC_PosC
     _inav(inav),
     _ahrs(ahrs),
     _pos_control(pos_control),
-    _attitude_control(attitude_control),
-    _wp_last_update(0),
-    _wp_step(0),
-    _track_length(0.0f),
-    _track_length_xy(0.0f),
-    _track_desired(0.0f),
-    _limited_speed_xy_cms(0.0f),
-    _track_accel(0.0f),
-    _track_speed(0.0f),
-    _track_leash_length(0.0f),
-    _slow_down_dist(0.0f),
-    _spline_time(0.0f),
-    _spline_time_scale(0.0f),
-    _spline_vel_scaler(0.0f),
-    _yaw(0.0f)
+    _attitude_control(attitude_control)
 {
     AP_Param::setup_object_defaults(this, var_info);