PHP notice in global-styles.php

[johngodley]

Using Gutenberg 8.3.0 I get this PHP warning on every front-end page access, as well as the editor:

Notice: Trying to access array offset on value of type bool in wp-content/plugins/gutenberg/lib/global-styles.php on line 212

The code carries on working regardless.

The line is:

$theme_gradients = get_theme_support( 'editor-gradient-presets' )[0];

Looking at the code for get_theme_support, it can return a false. It's probably worth adding a check for this before accessing it as an array.

It currently happens in master too.

This is for the theme Twenty Twenty. I note there is an update pending for this on my test site, so it's possible theme support was added. However, the notice should be fixed for themes that don't have support.

To reproduce
Steps to reproduce the behavior:

1. Install Gutenberg 8.3.0
2. Ensure you have PHP error reporting set to show notices
3. Load a front end page or the editor