AC_WPNav: allow target position on track to stop advancing

libraries/AC_WPNav/AC_WPNav.cpp

@@ -482,7 +482,7 @@ bool AC_WPNav::advance_wp_target_along_track(float dt)
         const float track_error = _pos_control.get_pos_error_cm().dot(track_direction);
         const float track_velocity = _inav.get_velocity_neu_cms().dot(track_direction);
         // set time scaler to be consistent with the achievable aircraft speed with a 5% buffer for short term variation.
-        track_scaler_dt = constrain_float(0.05f + (track_velocity - _pos_control.get_pos_xy_p().kP() * track_error) / curr_target_vel.length(), 0.1f, 1.0f);
+        track_scaler_dt = constrain_float(0.05f + (track_velocity - _pos_control.get_pos_xy_p().kP() * track_error) / curr_target_vel.length(), 0.0f, 1.0f);
     }
 
     // Use vel_scaler_dt to slow down the trajectory time