Error when Arabic script is used

I used Block Lab to create a certain type of “Alert Box” in a website. The website is bilingual, in Persian and English. The plugin works fine in English. In Persian also it works fine on the front-end. It shows everything correctly. But in the admin area, where I write the post, the block shows an error. When I click on it it shows up correctly but if it is unselected it shows an error.

This only happens when I enter the text in Arabic script. As soon as I replace the text with text in English the error goes away.

See the error here.