InvalidCastException: Column 'column_name' is null.

[zicjin]

System.InvalidCastException: Column 'site_id' is null.
   at Npgsql.ThrowHelper.ThrowInvalidCastException_NoValue(FieldDescription field)
   at Npgsql.Replication.PgOutput.ReplicationValue.GetStream()
   at Npgsql.Replication.PgOutput.ReplicationValue.GetTextReader()
   at PostgresOutbox.Subscriptions.Replication.EventDataMapper.ReadFromReplication(InsertMessage insertMessage, CancellationToken ct) in /src/czmpmedia/PostgresOutbox/Subscriptions/Replication/EventDataMapper.cs:line 15
   at PostgresOutbox.Subscriptions.Replication.EventDataMapper.ReadFromReplication(InsertMessage insertMessage, CancellationToken ct) in /src/czmpmedia/PostgresOutbox/Subscriptions/Replication/EventDataMapper.cs:line 12
   at PostgresOutbox.Subscriptions.ReplicationMessageHandlers.InsertMessageHandler.Handle(InsertMessage message, IReplicationDataMapper dataMapper, CancellationToken ct) in /src/czmpmedia/PostgresOutbox/Subscriptions/ReplicationMessageHandlers/InsertMessageHandler.cs:line 12
   at PostgresOutbox.Subscriptions.Subscription.Subscribe(SubscriptionOptions options, CancellationToken ct)+MoveNext() in /src/czmpmedia/PostgresOutbox/Subscriptions/Subscription.cs:line 69
   at PostgresOutbox.Subscriptions.Subscription.Subscribe(SubscriptionOptions options, CancellationToken ct)+MoveNext() in /src/czmpmedia/PostgresOutbox/Subscriptions/Subscription.cs:line 65
   at PostgresOutbox.Subscriptions.Subscription.Subscribe(SubscriptionOptions options, CancellationToken ct)+MoveNext() in /src/czmpmedia/PostgresOutbox/Subscriptions/Subscription.cs:line 65
   at PostgresOutbox.Subscriptions.Subscription.Subscribe(SubscriptionOptions options, CancellationToken ct)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()

I found relevant information:
https://stackoverflow.com/a/38930847/346701
"In ADO.NET, you need to check for a null value with reader.IsDBNull(0) before actually getting the value."
But the TextReader here does not have the IsDBNull() method.