Category on the portal page doesn't show space tiles in v2.18.6

The space tiles are not showing up on the portal if the category feature is used with the setting:

portal.noCategoryDefined=all

Steps to reproduce:

1. Create a viewport collection of spaces

2. apply the help center theme on the root space

3. open the theme-settings.properties file

4. define 2 categories and apply spaces to it

5. set the property portal.noCategoryDefined to "all"

6. Save

7. open the portal in the viewport

Expected:

The space tiles are shown in their categories.

Actual:

Only the categories are shown, but not the space tiles.