Project preview not working (project gadget)

Description

Prerequisite: Disable project mode in web.config.

Steps to reproduce:

1. Make sure project mode is disabled.
2. Create a project.
3. Add a page to the project using the project gadget.
4. Click the 'Toggle view settings' button ("the eye").
5. Click the 'View as if this project was published' button.

Expected
A list of available projects opens.

Actual
Nothing happens.