BC break in 3.77: Impossible to access an attribute ("translationDomain") on a boolean variable ("")

[dmaicher]

Sonata packages

$ composer show --latest 'sonata-project/*'
sonata-project/admin-bundle              3.77.0 3.77.0 The missing Symfony Admin Generator
sonata-project/block-bundle              4.4.0  4.4.0  Symfony SonataBlockBundle
sonata-project/cache                     2.0.1  2.0.1  Cache library
sonata-project/doctrine-extensions       1.9.1  1.10.1 Doctrine2 behavioral extensions
sonata-project/doctrine-orm-admin-bundle 3.24   3.24   Integrate Doctrine ORM into the SonataAdminBundle
sonata-project/exporter                  2.4.1  2.4.1  Lightweight Exporter library
sonata-project/form-extensions           1.6.0  1.6.0  Symfony form extensions
sonata-project/twig-extensions           1.4.1  1.4.1  Sonata twig extensions

Symfony packages

$ composer show --latest 'symfony/*'
symfony/asset                      v4.4.15 v4.4.15 Symfony Asset Component
symfony/browser-kit                v4.4.15 v4.4.15 Symfony BrowserKit Component
symfony/cache                      v4.4.10 v4.4.15 Symfony Cache component with PSR-6, PSR-16, and tags
symfony/cache-contracts            v2.2.0  v2.2.0  Generic abstractions related to caching
symfony/config                     v4.4.15 v4.4.15 Symfony Config Component
symfony/console                    v4.4.15 v4.4.15 Symfony Console Component
symfony/css-selector               v4.4.15 v4.4.15 Symfony CssSelector Component
symfony/debug                      v4.4.15 v4.4.15 Symfony Debug Component
symfony/debug-bundle               v4.4.15 v4.4.15 Symfony DebugBundle
symfony/dependency-injection       v4.4.15 v4.4.15 Symfony DependencyInjection Component
symfony/deprecation-contracts      v2.2.0  v2.2.0  A generic function and convention to trigger deprecation notices
symfony/doctrine-bridge            v4.4.15 v4.4.15 Symfony Doctrine Bridge
symfony/dom-crawler                v4.4.15 v4.4.15 Symfony DomCrawler Component
symfony/error-handler              v4.4.15 v4.4.15 Symfony ErrorHandler Component
symfony/event-dispatcher           v4.4.15 v4.4.15 Symfony EventDispatcher Component
symfony/event-dispatcher-contracts v1.1.9  v2.2.0  Generic abstractions related to dispatching event
symfony/expression-language        v4.4.15 v4.4.15 Symfony ExpressionLanguage Component
symfony/filesystem                 v4.4.15 v4.4.15 Symfony Filesystem Component
symfony/finder                     v4.4.15 v4.4.15 Symfony Finder Component
symfony/form                       v4.4.15 v4.4.15 Symfony Form Component
symfony/framework-bundle           v4.4.15 v4.4.15 Symfony FrameworkBundle
symfony/http-client-contracts      v2.3.1  v2.3.1  Generic abstractions related to HTTP clients
symfony/http-foundation            v4.4.15 v4.4.15 Symfony HttpFoundation Component
symfony/http-kernel                v4.4.15 v4.4.15 Symfony HttpKernel Component
symfony/inflector                  v4.4.15 v4.4.15 Symfony Inflector Component
symfony/intl                       v4.4.15 v4.4.15 A PHP replacement layer for the C intl extension that includes additional data from the ICU library.
symfony/mime                       v4.4.15 v4.4.15 A library to manipulate MIME messages
symfony/monolog-bridge             v4.4.15 v4.4.15 Symfony Monolog Bridge
symfony/monolog-bundle             v3.6.0  v3.6.0  Symfony MonologBundle
symfony/options-resolver           v4.4.15 v4.4.15 Symfony OptionsResolver Component
symfony/phpunit-bridge             v5.1.7  v5.1.7  Symfony PHPUnit Bridge
symfony/polyfill-ctype             v1.18.1 v1.18.1 Symfony polyfill for ctype functions
symfony/polyfill-intl-grapheme     v1.18.1 v1.18.1 Symfony polyfill for intl's grapheme_* functions
symfony/polyfill-intl-idn          v1.18.1 v1.18.1 Symfony polyfill for intl's idn_to_ascii and idn_to_utf8 functions
symfony/polyfill-intl-normalizer   v1.18.1 v1.18.1 Symfony polyfill for intl's Normalizer class and related functions
symfony/polyfill-php80             v1.18.1 v1.18.1 Symfony polyfill backporting some PHP 8.0+ features to lower PHP versions
symfony/process                    v4.4.15 v4.4.15 Symfony Process Component
symfony/property-access            v4.4.15 v4.4.15 Symfony PropertyAccess Component
symfony/property-info              v4.4.15 v4.4.15 Symfony Property Info Component
symfony/proxy-manager-bridge       v4.4.15 v4.4.15 Symfony ProxyManager Bridge
symfony/psr-http-message-bridge    v2.0.2  v2.0.2  PSR HTTP message bridge
symfony/routing                    v4.4.15 v4.4.15 Symfony Routing Component
symfony/security                   v4.4.15 v4.4.15 Symfony Security Component
symfony/security-acl               v3.1.0  v3.1.0  Symfony Security Component - ACL (Access Control List)
symfony/security-bundle            v4.4.15 v4.4.15 Symfony SecurityBundle
symfony/serializer                 v4.4.15 v4.4.15 Symfony Serializer Component
symfony/service-contracts          v2.2.0  v2.2.0  Generic abstractions related to writing services
symfony/stopwatch                  v4.4.15 v4.4.15 Symfony Stopwatch Component
symfony/string                     v5.1.7  v5.1.7  Symfony String component
symfony/swiftmailer-bundle         v3.2.4  v3.5.1  Symfony SwiftmailerBundle
symfony/templating                 v4.4.15 v4.4.15 Symfony Templating Component
symfony/translation                v4.4.15 v4.4.15 Symfony Translation Component
symfony/translation-contracts      v2.3.0  v2.3.0  Generic abstractions related to translation
symfony/twig-bridge                v4.4.15 v4.4.15 Symfony Twig Bridge
symfony/twig-bundle                v4.4.15 v4.4.15 Symfony TwigBundle
symfony/validator                  v4.4.15 v4.4.15 Symfony Validator Component
symfony/var-dumper                 v4.4.15 v4.4.15 Symfony mechanism for exploring and dumping PHP variables
symfony/var-exporter               v4.4.15 v4.4.15 A blend of var_export() + serialize() to turn any serializable data structure to plain PHP code
symfony/web-profiler-bundle        v4.4.15 v4.4.15 Symfony WebProfilerBundle
symfony/webpack-encore-bundle      v1.7.3  v1.7.3  Integration with your Symfony app & Webpack Encore!
symfony/yaml                       v4.4.15 v4.4.15 Symfony Yaml Component

PHP version

$ php -v
PHP 7.4.11 (cli) (built: Oct  8 2020 17:32:43) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.11, Copyright (c), by Zend Technologies

Subject

Since 3.77 I have this issue:

For me nested_field.vars['sonata_admin'].admin is false.

Pretty sure its caused by #6401

Steps to reproduce

Add one to many relation inline edit table.

[VincentLanglet]

Do you want to make a PR @dmaicher ?