First time the defaultTheme is not selected

Starting Theia the very first time, the workbench.colorTheme is not set in settings.json
And the defaultTheme is set to a to be loaded theme extension.
In this situation Theia has been started in the fallback theme which is dark.

I did some debugging and noticed that afther that new theme extension has beenloaded, theming.register adds the new theme to this.themes. But that new theme is not activated.

@Jaap which version are you using, there has been a recent fix to set default values for both the colorTheme and iconTheme. You can try master to verify if the change is working correctly for your use-case:

You should register the default theme in frontend module immediately after import section.

will check it