String as a second argument won't appear in logs

[Ko1103]

Bug Description

How to reproduce

const logger = new Logger();
const err = new Error('This is second argument');

logger.log('This is message.', err.message);  // show `This is message.` only.

Expected behavior

Shows both, like

logger.log('This is message.', err.message);  // show `This is message. This is second argument`.

[Ko1103]

Add delimiter for better readability. - as delimiter.

// show `This is message. - This is second argument`.