Unable to save a logo in Help Center

Steps to reproduce:

1. Go to Help Center in Customer Portal https://<instance-name>/servicedesk/customer/portals?customize=true
2. Tick on Use a logo
3. Choose the attached image within this ticket as a logo
4. Click Save Changes button

Expected Behavior:
Logo should be changed with the attached image/logo.

Current Behavior:
Logo is not saved and it's displaying the Help Center Name

Additional details
The bug seems to happen only when a user try to upload a white logo with a transparent background

Workaround
Edit the image before the upload changing the transparent background to the color of the topbar in the Service Desk portal.