Multiple email addresses for notifications – wrong output

After entering two email addresses for email notifications the value in the text field is wrong.
Plugin version 2.9.4

Steps to reproduce:
1. Enter two email addresses for email notifications.
2. Klick the Save button.

Actual behaviour:
The comma disappears and also the @ sign of the second address, like:
mail@domain1.commaildomain2.com

Expected behaviour:
mail@domain1.com,mail@domain2.com