fixed aspnetboilerplate#5529: Allow UserId being null when a SignalR Hub is connected

Author: ismcagdas

src/Abp.AspNetCore.SignalR/AspNetCore/SignalR/Hubs/OnlineClientHubBase.cs

@@ -60,7 +60,7 @@ protected virtual IOnlineClient CreateClientForCurrentConnection()
                 Context.ConnectionId,
                 GetIpAddressOfClient(),
                 Context.GetTenantId(),
-                Context.GetUserId()
+                Context.GetUserIdOrNull()
             );
         }