Collection named 'NUL' is not recognized / saved.

When a collection is named NUL, it will appear in the editor but does not get saved when the editor shuts down. When the project is restarted, the NUL collection is removed.

1. Open UE4 Editor (any project)
2. In the Content Browser, click View Options and enable Show Collection
3. In the Content Browser sources panel, click the plus button to add Local Collection
4. Name the collection 'NUL' and press enter
5. Save and restart the editor

Result:
Upon editor restart, the NUL collection has been removed from the content browser

Expected:
Collection is saved and available upon editor restart. Or, if NUL is a restricted name, editor warns that NUL cannot be used as a name.