Fixed customer export error on customer grid page.

[Taku-Yamashita]

I got the below error when I try to export customer data as CSV on a customer grid page.

Notice: Undefined index: listing_top in /xxx/vendor/magento/module-ui/Model/Export/MetadataProvider.php on line 224

↓$childComponents has order numbers as array keys instead of string like 'listing_top' when I enable CommunityEngineering_JapaneseAddress module.

Magento\Ui\Model\Export\MetadataProvider

223 $childComponents = $component->getChildComponents();
224 $listingTop = $childComponents['listing_top'];

The reason is that the below method changes array keys to order numbers.

CommunityEngineering\JapaneseAddress\Plugin\Ui\View\Element\PartiallyConfiguredUiComponent::afterGetChildComponents

[magento-cicd2]

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