Plane: fixed bug in rangefinder landing

introduced with QLAND change

ArduPlane/altitude.cpp

@@ -557,7 +557,6 @@ float Plane::rangefinder_correction(void)
 void Plane::rangefinder_height_update(void)
 {
     float distance = rangefinder.distance_cm()*0.01f;
-    float height_estimate = 0;
     if ((rangefinder.status() == RangeFinder::RangeFinder_Good) && home_is_set != HOME_UNSET) {
         if (!rangefinder_state.have_initial_reading) {
             rangefinder_state.have_initial_reading = true;
@@ -596,14 +595,14 @@ void Plane::rangefinder_height_update(void)
     if (rangefinder_state.in_range) {
         // base correction is the difference between baro altitude and
         // rangefinder estimate
-        float correction = relative_altitude() - height_estimate;
+        float correction = relative_altitude() - rangefinder_state.height_estimate;
 
 #if AP_TERRAIN_AVAILABLE
         // if we are terrain following then correction is based on terrain data
         float terrain_altitude;
         if ((target_altitude.terrain_following || g.terrain_follow) && 
             terrain.height_above_terrain(terrain_altitude, true)) {
-            correction = terrain_altitude - height_estimate;
+            correction = terrain_altitude - rangefinder_state.height_estimate;
         }
 #endif    
 
@@ -617,7 +616,7 @@ void Plane::rangefinder_height_update(void)
             if (fabsf(rangefinder_state.correction - rangefinder_state.initial_correction) > 30) {
                 // the correction has changed by more than 30m, reset use of Lidar. We may have a bad lidar
                 if (rangefinder_state.in_use) {
-                    gcs_send_text_fmt(MAV_SEVERITY_INFO, "Rangefinder disengaged at %.2fm", (double)height_estimate);
+                    gcs_send_text_fmt(MAV_SEVERITY_INFO, "Rangefinder disengaged at %.2fm", (double)rangefinder_state.height_estimate);
                 }
                 memset(&rangefinder_state, 0, sizeof(rangefinder_state));
             }