Fix #4803: Incorrect return value from Product Attribute Repository

[julian-van-drielen]

Description

Forward pull of PR #15688

@vkublytskyi Suggested this fix to resolve issue 4803,

Fixed Issues (if relevant)

1. Incorrect return value from Product Attribute Repository #4803: Incorrect return value from Product Attribute Repository

Manual testing scenarios

1. This can be tested by calling the function Magento\Catalog\Model\Product\Attribute\Repository::getCustomAttributesMetadata and check return type.

Contribution checklist

• [✓] Pull request has a meaningful description of its purpose
• [✓] All commits are accompanied by meaningful commit messages
• [✓] All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[orlangur]

@cream-julian please fix coding style and force push as a single commit.

[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-2642 has been created to process this Pull Request

[magento-engcom-team]

Hi @cream-julian. Thank you for your contribution.
We will aim to release these changes as part of 2.2.7.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.