Customizer errors when control is associated with non-existing section

[prajaktag]

Get this js error while creating new menu from themes customiser - Uncaught TypeError: Cannot read property 'open' of undefined

Here is screenshot - ​https://goo.gl/gVaxBU

• Uncaught TypeError: Cannot read property 'open' of undefined

The theme is ​One Page X with beta 3 wordpress.

[westonruter]

The error when attempting to add a nav menu item is probably a side effect of the first error related to unsync being undefined.

[westonruter]

The reason for the error is that theme is doing $wp_customize->remove_section( 'header_image') and $wp_customize->add_section( 'background_image'), but it is not subsequently changing the section for the controls that were in the header_image section. So the background_repeat control is getting added to the Customizer without a containing section. Because of this, the embedded deferred is never resolved because of this: ​https://github.com/WordPress/wordpress-develop/blob/a33d615/src/wp-admin/js/customize-controls.js#L3578-L3590

And since the control.linkElements() is currently being called once embedded is deferred, the elements then never get created. And this is why the error is happening.

[westonruter]

​https://github.com/xwp/wordpress-develop/pull/293

[rinkuyadav999]

Hi @westonruter

This patch fixed both issues. Menu, Theme Changes in customize.

Thanks

[westonruter]

In 42024:

Customize: Link elements prior to embedding to prevent possible errors when a control is associated with a non-existent section.

Fixes issue specifically with attempting to access an orphaned control's elements immediately after it has been added. Normally this would not happen because a control would not be registered without a section, and also a control should only be interacted with once its embedded deferred has been resolved.

Also harden logic for gathering list of deferred setting IDs.

See #37964.
Fixes #42330.