Portfolio option not displaying Customizer

A user in the following WordPress.org forum thread reported that the Portfolio option is missing when they navigate to Appearance > Customize:

https://wordpress.org/support/topic/page-title-at-the-portfolio-archive-page/

The user only has three plugin (Akismet, Hello Dolly, and Jetpack) active. Jetpack's Custom Content Type module is active and they're able to see the portfolio items they've added when adding /portfolio to the end of their site's URL.

**Theme** is displaying in place of **Portfolio** in the Customizer for the user. They're only seeing the top two options that usually display under **Portfolio** there. I've highlighted the two options that are displaying to them here:

The following is a screenshot of the JavaScript errors in their console:

Let me know if/what extra information would be helpful on this.

Start with the linked WordPress.org forum thread and reproduce the issue in Appearance > Customize with Jetpack's Custom Content Type module active and portfolio items present. Inspect the browser console errors shown in the issue and trace the Customizer behavior; done means Portfolio appears instead of Theme and its expected options are available.

Written by the indexing model from the issue text.