Not compatible with config_split module

abhishek_gupta1 → made their first commit to this issue’s fork.

@khaldoon_masud, I have fixed the issue. Please kindly review the MR

@abhishek_gupta1 That patch did not fix the issue, because the error is thrown in the upper IF condition not in the ELSE condition:

if ($inline_entity_form_parents = ConditionalFieldsFormHelper::findInlineEntityFormParentsForElement($full_form, $field)) {
          $form = &NestedArray::getValue($full_form, $inline_entity_form_parents['element_parents']);

          // Remove outer forms from field parents arrays.
          $field = ConditionalFieldsFormHelper::fieldRemoveInlineEntityFormParents($field, $inline_entity_form_parents);

          $ief_entity = $form["#entity"];
          $bundle = $ief_entity->bundle();
          $entity_type = $ief_entity->getEntityTypeId();
        }
        else {
          $form = &$full_form;
          $bundle = $entity->bundle();
          $entity_type = $entity->getEntityTypeId();

          /**
           * @deprecated Not actual from Drupal 8.7.0.
           * Media entity returns the actual bundle object, rather than id
           */
          if (is_object($bundle) && method_exists($bundle, 'getPluginId')) {
            $bundle = $bundle->getPluginId();
          } elseif (is_object($bundle) && method_exists($bundle, 'bundle')) {
            $bundle = $bundle->bundle();
          }
        }

$ief_entity is NULL cause $form["#entity"] is NULL, thus $ief_entity->bundle() throws an error.

The fix should be something like:

if (!isset($form["#entity"])) {
 return;
}

On a site with both conditional_fields and config_split installed, I visited admin/config/development/configuration/config-split/add and did not see any error message. There must be more required to generate the error.

Upon attempting to replicate the reported issue, I have followed the outlined steps, which involved installing both the Config Split and Conditional Field modules and navigating to the specified configuration page at "admin/config/development/configuration/config-split/add." However, I was unable to encounter the issue as described.
Should have any additional details or steps to provide.

This problem is caused by having applied the patch (in my case) https://www.drupal.org/files/issues/2023-10-30/2856720-support-for-inlin... → .

Removed the patch, it works correctly.

As of #6/#7 and me testing I cannot reproduce this issue. All other reports rather tend to make clear that this issue is caused by other circumstances. Feel free to reopen if more/better information to reprocude this issue can be provided. Thanks for all the efforts in here!

And also, please provide patches and MR always against latest dev. Thanks for understanding.

Install modules:
drupal/conditional_fields
drupal/entity_translation_sync

Set a conditional field to some Content Type.
Then go to edit page to create/edit some Node and in a tab Entity Translation Sync you can see error:

The website encountered an unexpected error. Try again later.

Error: Call to protected method Drupal\entity_translation_sync\Form\EntityTranslationSyncForm::getEntity() from scope Drupal\conditional_fields\ConditionalFieldsElementAlterHelper in Drupal\conditional_fields\ConditionalFieldsElementAlterHelper->afterBuild() (line 53 of modules/contrib/conditional_fields/src/ConditionalFieldsElementAlterHelper.php).