Server error (500) when there's a single database connected and admin user is not a collaborator

[pavish]

Description

• Create a database if nothing exists. Make sure there's only one database at the end.
• Open the database, remove yourself from the collaborator list.
• Refresh the page. Or change url to homepage on the browser url bar (eg., localhost).
• Notice a server error.
• This also happens when directly visiting any database url where the user is not a collaborator, and even when visiting a url for a non-existent database eg, (http://localhost/db/10000/).

Probable cause

• Since the user is not a collaborator on the database, creating the common_data would fail causing this 500.

Expected behavior

• If the user is an admin, there should not be an error and the UI should show the database page with the error/add-yourself-as-a-collaborator message inside the page.
• If the user is not an admin, the url should redirect to /databases.

[Anish9901]

Fixed in #3948