Fix PHP Type error in Header block class when Welcome Text is empty

[TuVanDev]

Description (*)

This pull request includes fixes for #37208
TypeError: addslashes(): Argument #1 ($string) must be of type string, null given in /var/www/html/app/vendor/magento/framework/Escaper.php:440

Fixed Issues (if relevant)

1. Fixes Error 500 when design/header/welcome is null #37208

Manual testing scenarios (*)

1. ...
2. ...

Questions or comments

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)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

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[TuVanDev]

@magento give me test instance

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Hi @Viper9x. Thank you for your request. I'm working on Magento instance for you.

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Hi @Viper9x, here is your Magento Instance: https://d87201baa9909e2b845897db7ebf753b.instances-prod.magento-community.engineering
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[TuVanDev]

@magento run all tests

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The requested builds are added to the queue. You should be able to see them here within a few minutes. Please re-request them if they don't show in a reasonable amount of time.

[leonhelmus]

Yes, this does resolve the issue that i fast as well when upgrading to version 2.4.6

[engcom-Lima]

@magento run Functional Tests EE , Functional Tests CE , Functional Tests B2B

[magento-automated-testing]

The requested builds are added to the queue. You should be able to see them here within a few minutes. Please re-request them if they don't show in a reasonable amount of time.

[magento-automated-testing]

The requested builds are added to the queue. You should be able to see them here within a few minutes. Please re-request them if they don't show in a reasonable amount of time.

[engcom-November]

✔️ QA Passed

Preconditions: -
Install fresh Magento 2.4-develop with PHP 8.1 and 2.4.6 project-community-edition

Manual testing scenario:
Error 500, with exception when accessing the front end on removing Header text from Content - Design - Configuration for main website store view

Before: ✖️ 
Issue not reproducible on 2.4-develop but is reproducible on 2.4.6 project-community-edition

After: ✔️
Issue not reproducible on both 2.4.6 and 2.4-develop instances.

As builds are getting failed, moving this PR to Extended Testing.

[TuVanDev]

There is a commit 4b5c1dc merged to 2.4-develop branch to fix "the welcome message contains single quote character", it also inadvertently solved the issue this PR trying to fix (#37208) since __() method return \Magento\Framework\Phrase which also force change the type of the text to string , so I'll close this PR as it no longer necessary.