v11 Pro Upgrade Problem: What is marketing_extras_content supposed to be?

I upgraded my development instance to v11.0.0. Sugar Professional On Site.

The application is unuseable because of a PHP Fatal Error in 

src/Marketing/MarketingExtrasContent.php line: 68

The getMarketingContentConfig() function is supposed to return an array but returns nothing, as far as I've been able to tell, this is because there is no 'marketing_extras_content' in my config file.

    protected function getMarketingContentConfig(): array
    {
        if (empty($this->marketingContentConfig)) {
            $this->marketingContentConfig = $this->getMarketingExtrasHelper()->getSugarConfig('login_page')['marketing_extras_content'];
        }

        return $this->marketingContentConfig;
    }

The only config entries for marketing extras are:

  'marketing_extras_enabled' => true,
  'marketing_extras_url' => 'https://marketing.sugarcrm.com/content',

What is marketing_extras_content supposed to be?

Thanks,
Francesca