Describe the bug
I have clone this repo and try to use it. It works well except the thumbnails in the left sidebar. I cannot see any images there. However, when I click up/down button on the toolbar, I can change image successfully.

I try to debug and stuck at the editorSideBar.tsx. I don't know why the List element not call this.rowRenderer function. I try to do console.log at the rowRenderer function but nothing print out.

Screenshots

Desktop (please complete the following information):

• OS: Ubuntu 16.04
• Browser Chrome