manual WH cleanup when WH exists but building doesn't

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

@@ -528,8 +528,15 @@ public class PlaceAssetMsgHandler extends AbstractClientMsgHandler {
             return false;
 
         if (cityObject.warehouse != null) {
+            if(cityObject.warehouse.building != null) {
+                //warehosue has a building already, warehouse still should exist
                 PlaceAssetMsg.sendPlaceAssetError(origin, 50, "");  //"You can only have one warehouse"
                 return false;
+            }else{
+                //warehouse has no building and needs a cleanup
+                DbManager.WarehouseQueries.DELETE_WAREHOUSE(cityObject.warehouse);
+                cityObject.warehouse = null;
+            }
         }
 
         // Create the warehouse object and it's entry in the database