[Backport] Fixed add to wishlist issue on product price 0

[sreichel]

Description

Backport #16537

Fixed Issues (if relevant)

1. Issue in adding the wishlist of "zero price" product.  #16479:Issue in adding the wishlist of "zero price" product

Manual testing scenarios

1. Login as a customer in front end of the website.
   2, Open product with zero price
   3, Click on the wishlist button in the product

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)

[magento-engcom-team]

Hi @sreichel. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

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[magento-engcom-team]

Hi @sreichel. 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.