Deprecated function: pathinfo() on template_preprocess_image_style

Problem/Motivation

After upgrading to PHP 8.1, we get a deprecated warning when the Image style Uri is not set on template_preprocess_image_style.

%type: @message in %function (line %line of %file) @backtrace_string. | a:6:{s:5:"%type";s:19:"Deprecated function";s:8:"@message";O:25:"Drupal\Core\Render\Markup":1:{s:9:" * string";s:77:"pathinfo(): Passing null to parameter #1 ($path) of type string is deprecated";}s:9:"%function";s:45:"Drupal\image\Entity\ImageStyle->supportsUri()";s:5:"%file";s:78:"/mnt/www/html/myproject/docroot/core/modules/image/src/Entity/ImageStyle.php";s:5:"%line";i:385;s:17:"@backtrace_string";s:16143:"#0 /mnt/www/html/myproject/docroot/core/includes/bootstrap.inc(346): _drupal_error_handler_real(8192, 'pathinfo(): Pas...', '/mnt/www/html/d...', 385)
#1 [internal function]: _drupal_error_handler(8192, 'pathinfo(): Pas...', '/mnt/www/html/d...', 385)
#2 /mnt/www/html/myproject/docroot/core/modules/image/src/Entity/ImageStyle.php(385): pathinfo(NULL, 4)
#3 /mnt/www/html/myproject/docroot/core/modules/image/image.module(274): Drupal\image\Entity\ImageStyle->supportsUri(NULL)
#4 /mnt/www/html/myproject/docroot/core/lib/Drupal/Core/Theme/ThemeManager.php(287): template_preprocess_image_style(Array, 'image_style', Array)
#5 /mnt/www/html/myproject/docroot/core/lib/Drupal/Core/Render/Renderer.php(422): Drupal\Core\Theme\ThemeManager->render('image_style', Array)
#6 /mnt/www/html/myproject/docroot/core/lib/Drupal/Core/Render/Renderer.php(201): Drupal\Core\Render\Renderer->doRender(Array, false)

This seems because the URI is not defined on the variable URI when the method supportsUri is called, function template_preprocess_image_style.
https://git.drupalcode.org/project/drupal/-/blob/9600a0b13a4301c0071dad3...

....
if ($style->supportsUri($variables['uri'])) {
    $variables['image']['#uri'] = $style->buildUrl($variables['uri']);
  }
  else {
...

Steps to reproduce

Try to generate an image style without URI (can be tried with a render array).

Proposed resolution

Check if the URI is set before calling supportURI, because the method expects a string, or change the param to string|null and verify there is the param is a string.

It is possible that this fix conflicts with issues:

• null in template_preprocess_image_style()
• ">Call to a member function transformDimensions() on null in template_preprocess