[4.3] Fix Media Field with Windows directory separator in value

[joomdonation]

Pull Request for Issue #39203.

Summary of Changes

Sometime, on a window system, value stored for a media form field has this format images\headers\banner.jpg and it will throw warning and there will be notice like below when you edit the record contains that field:

Notice: Undefined offset: 0 in ...\libraries\src\Form\Field\MediaField.php on line 294

This PR just fixes that notice.

Testing Instructions

If you want to fully re-procedure the issue, you need to have Joomla setup on windows and follow instructions at #39203 (comment) to see the issue. However, there is a simple way to re-procedure it :

1. Add the line of code below after this line https://github.com/joomla/joomla-cms/blob/4.2-dev/libraries/src/Form/Field/MediaField.php#L263 . That will fake name of the image file in window directory separator format

$this->value = 'images\headers\banner.jpg';

Actual result BEFORE applying this Pull Request

You see notice like below:

Notice: Undefined offset: 0 in ...\libraries\src\Form\Field\MediaField.php on line 294

Expected result AFTER applying this Pull Request

No notice anymore.

[jwaisner]

I have tested this item ✅ successfully on 546b4c4

Looks good. Tested on Windows 11.

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[robbiejackson]

I've tested this and can confirm that it fixes the original issue 39203 which I raised.

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[richard67]

I've tested this and can confirm that it fixes the original issue 39203 which I raised.

@robbiejackson Please use the blue "Test this" button at the top left corner in the issue tracker, then select your test result and then submit, so your test is properly counted. Thanks in advance.

[robbiejackson]

I have tested this item ✅ successfully on 546b4c4

Tested using images uploaded from a front-end form and which resulted in the images being given pathnames which were of the Windows format (with backslashes). This included tests for wben the Media Global Config "Path to Images Folder" was set to a Windows-format pathname images\photos, as well as a linux format pathname, and the images uploaded were saved to that folder.

These image files were then treated as media form fields in the admin backend, and the tests confirmed that the fields displayed and were editable ok, both before and after the associated records (with the image pathnames) were saved to the database.

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[richard67]

RTC

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[laoneo]

Thank you!