DivisionByZeroError in viewElements() when an image item has no stored dimensions

Problem/Motivation

EasyLqpImagesFormatter::viewElements() derives an aspect ratio
from the image item's stored dimensions:

$original_width = $elements[$delta]['#item_attributes']['width']->value();
$original_height = $elements[$delta]['#item_attributes']['height']->value();
$aspect_ratio = $original_width / $original_height;
$width = $elements[$delta]['#srcset'][0]['width'];
$height = floor($width / $aspect_ratio);

Those values come from the image field item, via
$element['#item']->getValue()['height'] ?? NULL earlier in the
same method. An image item with no stored height yields 0 or
NULL, and the division then throws:

DivisionByZeroError: Division by zero in
Drupal\easy_lqp\Plugin\Field\FieldFormatter\EasyLqpImagesFormatter->viewElements()
(line 234 of
modules/contrib/easy_lqp/src/Plugin/Field/FieldFormatter/EasyLqpImagesFormatter.php)

This is an uncaught error rather than a warning, so it fatals the render of
the page containing the image.

Image items can legitimately lack stored dimensions — for example when a file
was attached by a migration or programmatically without the width and height
columns being populated, or when the referenced file is missing from the file
system at the time the item was saved.

Steps to reproduce

1. Configure an image field display to use the "Easy LQP Images" formatter with
   the "Scale" image handling option.
2. Ensure an image field item exists whose stored height is
   0 or NULL.
3. View a page rendering that item. The request fatals with
   DivisionByZeroError.

Proposed resolution

Guard the calculation and leave the height unset when either dimension is
missing, so the resizer JavaScript still supplies the final dimensions:

$original_width = $elements[$delta]['#item_attributes']['width']->value();
$original_height = $elements[$delta]['#item_attributes']['height']->value();
$width = $elements[$delta]['#srcset'][0]['width'];
// An image item with no stored dimensions yields a zero height, which
// would make the aspect ratio calculation divide by zero.
if (empty($original_height) || empty($original_width)) {
  $height = NULL;
}
else {
  $height = floor($width / ($original_width / $original_height));
}

The subsequent lines already overwrite width and height with the original
values for the low quality placeholder, so nothing downstream depends on the
intermediate $height when it cannot be computed.

Remaining tasks

• Review the merge request
• Commit and tag a release

User interface changes

None.

API changes

None.

Data model changes

None.