Accessing a document from a public shared folder does not ask for guest username

[elzody]

Describe the bug
When a document is inside of a publicly shared folder, guest users who access the document are not asked to input a guest username. It simply defaults to "Anonymous Guest." On the other hand, when accessing a document which was publicly shared individually, it asks for a guest username, as expected.

To Reproduce
Steps to reproduce the behavior:

1. Create a folder in the Files app and insert a blank document into it
2. Create a public share link for the folder
3. Open the shared folder (not logged in)
4. Open the document inside
5. It will open the document directly

Expected behavior
The expect behavior is that, when opening a document as a guest, no matter where the document is (within a shared folder, or shared individually), the user will be asked to input a guest username. This makes identifying people much easier, as when there are several people editing, you don't know who it is.

Client details:

• Browser: Firefox, Chrome
• Version: Affects v27 - v30
• Device: Desktop

Notes
Probably related to this pull request. Also worth to mention this pull request