Skip the warehouse delete when the owner destroys warehouse rubble

city.warehouse is already null after a combat destruction, which threw in
DELETE_WAREHOUSE. If a new warehouse was placed it would have deleted that
one instead, so only a live (rank != -1) warehouse clears city.warehouse.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/engine/net/client/handlers/DestroyBuildingHandler.java

@@ -98,9 +98,12 @@ public class DestroyBuildingHandler extends AbstractClientMsgHandler {
                 return true;
 
             Warehouse.destroyedWarehouses.remove(building.getObjectUUID());
-            DbManager.WarehouseQueries.DELETE_WAREHOUSE(city.warehouse);
 
-            city.warehouse = null;
+            // Rubble no longer owns city.warehouse, which may be null or a newly placed warehouse
+            if (city.warehouse != null && building.getRank() != -1) {
+                DbManager.WarehouseQueries.DELETE_WAREHOUSE(city.warehouse);
+                city.warehouse = null;
+            }
 
         }