message: Fix bug with log level set to trace in debug mode
diff: @@ -420,7 +420,7 @@ void Changeset::Reflector::operator()(const Instruction::AddColumn& p) const
  m_tracer.field("type", p.type);
  }
  else {
  - m_tracer.field("type", "Mixed");
  + m_tracer.field("type", Instruction::Payload::Type::Null);
  }
  m_tracer.field("nullable", p.nullable);
  m_tracer.field("collection_type", p.collection_type);
  