Fix unclear 'Error during deserialization: null' messages

Author: ark-1

serialization/src/main/kotlin/SerializationIntegration.kt

@@ -98,7 +98,7 @@ public class SerializationIntegration : JupyterIntegration(){
 "jsonDeserializer.decodeFromString<$className>(\"\"\"$escapedJson\"\"\")"
  ).name
  } catch (e:Exception){
- display("Error during deserialization: ${e.cause?.message}", id =null)
+ display("Error during deserialization: ${e.cause?.message?: e.message}", id =null)
 null
  }
  }