Add additional check if password hash is empty in auth process

[progreg]

Description

Added additional check for password hash if the customer was created without a password from admin area.

Fixed Issues

1. User created by admin cannot login #19060: User created by admin cannot login

Manual testing scenarios

1. Create customer at admin area (without password)
2. Try to login at frontend as a customer

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 @progreg. Thank you for your contribution
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[magento-engcom-team]

Hi @VladimirZaets, thank you for the review.
ENGCOM-3390 has been created to process this Pull Request

[magento-engcom-team]

Hi @progreg. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.

[salehawal]

i also found a isue in this methud, after changing the return value format it did work fine

public function isValidHash($password, $hash)
{
    $this->explodePasswordHash($hash);

    foreach ($this->getPasswordVersion() as $hashVersion) {
        $password = $this->hash($this->getPasswordSalt() . $password, $hashVersion);
    }

    $hash = $this->getPasswordHash();
    return Security::compareStrings(
        $password,
        $hash
    );
}