ImageThumbnail::getAsset() declares a non-nullable return type but the backing property is nullable

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Affected Version

2026.2

Affected capability

Assets

Steps to reproduce

1. Construct a thumbnail without a backing asset, which the API allows since ImageThumbnailTrait::$asset is declared ?Asset:

   $thumbnail = new \Pimcore\Model\Asset\Video\ImageThumbnail(null);

   (In practice this happens when a thumbnail is built from a raw path reference or the underlying asset can no longer be resolved.)

2. Call $thumbnail->getAsset() — directly, or indirectly by rendering the thumbnail via __toString() / getPath(), or through the ASSET_*_THUMBNAIL frontend events.

Actual Behavior

The method crashes inside itself:

TypeError: Pimcore\Model\Asset\Thumbnail\ImageThumbnailTrait::getAsset():
Return value must be of type Pimcore\Model\Asset, null returned

ImageThumbnailInterface::getAsset() and ImageThumbnailTrait::getAsset() both declare : Asset, which contradicts the nullable ?Asset $asset property they read from. Related call sites in the trait (getDimensions(), getFileSize()) also dereference the result unguarded.

Expected Behavior

getAsset() declares ?Asset, matching the property and the actual runtime behaviour, so callers can handle the absent-asset case instead of the getter throwing. Fixed by pimcore/pimcore#19277 (targets 2026.x, as widening a public API return type to nullable affects callers).