Impact defaultLocale on Authoring support

Steps to reproduce

1. Import Site configuration and website workspace as attached
2. Open the pages app of pageB
3. Delete the defaultLocale of the site config of siteB
4. open the pages app of pageB again 

Expected results

I would expect that the default locale has no impact on the language switch in the pages app. Because pageB has nl as fallback language, I would expect to see Dutch preselected.

Actual results

With defaultLocale:

Without defaultLocale:

Workaround

Development notes

Our Partner Dev5310 suggested a fix in the Ticket https://jira.magnolia-cms.com/browse/SUPPORT-13188

In my opinion this is not really working because without setting the defaultLocale you still get German preselected.

I tried to fix it by my own but i am not sure if this breaks something else. If we would change -> Class → info.magnolia.livecopy.i18n.LiveCopyI18nContentSupport (Line 89 - 92)

@Override
public Locale getFallbackLocale() {
    return masterLocale != null ? new Locale(masterLocale) : super.getFallbackLocale();
}

// INTO

@Override
public Locale getFallbackLocale() {
    return super.getFallbackLocale() != null ? super.getFallbackLocale() : new Locale(masterLocale);
}

The problem is gone without the need to set the defaultLocale.