b632b5c974
This changes the drawing in the tree interface panel so that panels always show the icon to collapse it, even if it is empty. This makes it more obvious when an item is a panel and not just a socket. Right now, this is not strictly necessary, because sockets can also be identified by their socket icon. However, that changes with #133936 where a panel can also have a (boolean) socket. Pull Request: https://projects.blender.org/blender/blender/pulls/135207