Improve empty states

Certain sections need the [empty states](https://www.toptal.com/designers/ux/empty-state-ux-design#:~:text=What%20Is%20an%20Empty%20State,there%20is%20nothing%20to%20display.) improved. These are 2 that I have found, but while I am reviewing the design of the DLP, I may find more:

**Sidebar (Other Versions)**

**Main Dandiset Content (Associated Projects)**

There are 2 options for solving this:
1. Hide the whole section if there is no content
2. Include help text letting the user know there is nothing there and a potential reason why

The second is my preference because it is the most informative for the users. If they're looking for that information and it is not there (like mentioned in 1) they will likely wonder why and the help text will solve their confusion without the need for them to spend effort trying to find the answer.