Warning: Undefined array key "context_visibility" when configuring section

Problem/Motivation

Seeing the following warning in watchdog log:

Warning: Undefined array key "context_visibility" in layout_builder_context_form_alter() (line 33 of /app/web/modules/contrib/layout_builder_context/layout_builder_context.module)

Steps to reproduce

Configuring a layout builder section that has not previously used Layout Builder Context and check PHP notices in the log.

Proposed resolution

Relevant line 33:

        $contexts = is_array($configuration["context_visibility"]) ? $configuration["context_visibility"] : [];

Just use the null coalescing operator, It's cleaner and does the trick.