We are upgrading from DXA 1.5 to 1.8 with Tridion Sites 9.1 and UDP 11.1
After upgraded to DXA 1.8 we are facing object reference not set to an instance error.
We have upgraded sdl.web.delivery references to 11.0 on WebApp
In the logs saw below exception
2019-12-09 14:19:37 DEBUG [Sdl.Web.Delivery.Broker.Querying.QueryImpl.ExecuteQuery] - Deserializer() Exception thrown: 'System.NullReferenceException' in App_Web_sdawx5dt.dll Model.**get** returned null
Also in the site.log file few more debug log says Property Schema.title cannot be mapped to a CM field of SemanticSchema 544 (Schema). Semantic properties: :title.
Any suggestion/advise would be helpful.