BulletSim: remove some errors on shutdown by moving terrain destruction until after physical object destruction. TerrainManager also made disposable and that feature used.

OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs

@@ -67,7 +67,7 @@ public abstract class BSTerrainPhys : IDisposable
 }
 
 // ==========================================================================================
-public sealed class BSTerrainManager
+public sealed class BSTerrainManager : IDisposable
 {
     static string LogHeader = "[BULLETSIM TERRAIN MANAGER]";
 
@@ -122,6 +122,11 @@ public sealed class BSTerrainManager
         MegaRegionParentPhysicsScene = null;
     }
 
+    public void Dispose()
+    {
+        ReleaseGroundPlaneAndTerrain();
+    }
+
     // Create the initial instance of terrain and the underlying ground plane.
     // This is called from the initialization routine so we presume it is
     //    safe to call Bullet in real time. We hope no one is moving prims around yet.
@@ -366,6 +371,9 @@ public sealed class BSTerrainManager
             {
                 PhysicsScene.Logger.ErrorFormat("{0} GetTerrainHeightAtXY: terrain not found: region={1}, x={2}, y={3}",
                         LogHeader, PhysicsScene.RegionName, tX, tY);
+                DetailLog("{0},BSTerrainManager.GetTerrainHeightAtXYZ,terrainNotFound,loc={1},base={2}",
+                                    BSScene.DetailLogZero, loc, terrainBaseXYZ);
+                Util.PrintCallStack();      // DEBUG DEBUG DEBUG
             }
         }
         lastHeight = ret;