"Assigned contexts were not satisfied" ContextException when rendering 'broken' section components expecting context

Problem/Motivation

Steps to reproduce:

1. Add an extra field for a node bundle in a module.
2. Add the extra field block to layout builder for the node bundle display defaults layout or in an override on a node of that bundle
3. Uninstall the module
4. View the node
5. Observe there is a ContextException error: "Assigned contexts were not satisfied"

It would be ideal to avoid the Exception and the broken plugin to display the missing plugin text instead.

Proposed resolution

Issue arises because in \Drupal\layout_builder\SectionComponent::getPluginId(), the context mapping that was original configured for the extra field block is being applied to the fallback "broken" block plugin, which has no context definitions.

Proposed solution is to check that the instantiated plugin isn't the fallback plugin before trying to apply the context mapping

Remaining tasks

Needs review and tests

User interface changes

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A

Original report by [username]

N/A