Twenty Seventeen: customize-controls.js incorrectly assumes theme_options section is always present

[westonruter]

Plugins can de-register panels, sections, controls, and settings that are registered by default by core and by themes. As such, themes should use the deferred pattern to interact with such constructs. This is particularly an issue in Twenty Seventeen and now it assumes the theme_options section is present.

Originally reported at ​https://github.com/xwp/wp-customizer-blank-slate/issues/8

[davidakennedy]

Thanks for the report and patch @westonruter! This looks good and worked well in my testing.

[davidakennedy]

In 39623:

Twenty Seventeen: Ensure functions in customize-controls.js don't count on Customizer sections always being present

Before, the code assumed the theme_options section is always present, but it can be removed by plugins. This way, if it is, no JavaScript errors occur.

Props westonruter.

Fixes #39335.

[westonruter]

Not 100% sure if this is the right procedure for bundled themes, but re-opening for committing into 4.7 branch.

[dd32]

Not 100% sure if this is the right procedure for bundled themes, but re-opening for committing into 4.7 branch.

FTR, yes, Twenty Seventeen fixes will need merging to the 4.7 branch too. @davidakennedy I'm happy to take care of that in one of my merge-storms.

[westonruter]

This commit [39623] was merged to the 4.7 branch in [39632] by @pento, though it had a typo in the ticket reference.