Redirect after login leads to incorrect path

[mtrezza]

New Issue Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am not just asking a question.
• [x] I have searched through existing issues.
• [x] I can reproduce the issue with the latest versions of Parse Server and Parse Dashboard.

Issue Description

When the login session of Parse Dashboard has expired, the redirection contains an incorrect URL with an additional slash.

Steps to reproduce

1. Open a new browser window, log in to Parse Dashboard and navigate to the _User class.
2. Delete all website data incl. cookies for the dashboard website in the browser settings.
3. Reload the website.
4. Browser URL shows login page with URL: https://example.com/login?redirect=/apps/app-name/browser/_User
5. Open a new browser tab in the same browser window, copy paste the URL above and log in.
6. Reload the first tab that shows the login page.
7. A redirection to URL https://example.com//apps/app-name/browser/_User occurs which leads to a 404 site.

Actual Outcome

The redirection URL in step 7 above contains an additional slash.

Expected Outcome

The redirection URL should not contain the additional slash.

Environment

Dashboard

• Parse Dashboard version: 6.0.0
• Browser (Safari, Chrome, Firefox, Edge, etc.): Safari

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