Problem/Motivation
The following error is generated when rendering an extra field block on a layout builder enabled page, when the extra field renders a block content entity.
Undefined array key "view_mode" in block_content_theme_suggestions_block_alter() (line 201 of core/modules/block_content/block_content.module)
Steps to reproduce
Add an extra field block to a layout builder enabled page for an extra field that renders a block content entity. Then view the page.
Proposed resolution
Change the code to extract the view mode from the content, instead of configuration. The view mode is present in content for both regular block plugins and for an extra field rendering a block content, while it is present in configuration for regular block plugins only.
User interface changes
None