Problem/Motivation
The sidebar in the Add or select Media Library widget is missing the proper styling in 10.2.x-dev and 11.x-dev:
In 10.1.x the styling looks correct:
Steps to reproduce
1. Add a media field to a content type.
2. Add two or more media types as reference type for the added media field.
3. Create a node for that content type
4. Attempt to attach a media item to the field.
5. The Media Library "widget" View will display. The left sidebar, showing the available media types, does not display the previous horizontal separators.