Steps to reproduce

1. Open Admincentral
2. Click Edit User Profile
3. Select Preferences tab
4. Enter "Europe/Zurich (Central European Standard Time)" text into Time Zone Field
5. Hit Tab

Actual behavior

The Time Zone value resets to the old value

Expected behavior

The Time Zone value should update to the newly entered value.

Additional info

Entering partial texts such as "Eur" or "Zu" should show filtered option list in the the Combobox, but no such filtered list is visible.

This bug may impact any field that is based on Combobox. A similar issue is reported on Vaadin by other people https://vaadin.com/forum/thread/16302265/combobox-loses-the-user-input-when-losing-focus-vaadin-8. A workaround would probably be needed to mitigate this issue until Vaadin comes with a fix for it.