Error when entered Style Editor

I got this error while working on a project as soon as I moved to the Style Editor page.
"An error has occurred in the script on this page:
Line: 133

Char: 27

Error: Unable to get value of the property 'offsetTop': object is null or undefined

Code: 0

URL: file:///C:/Program Files/PHPRunner6.0/StyleEditor/Runner/styleeditor/listboxes/base_listbox.js
Do you want to continue running scripts in this page?
Yes / No"