Adjust the owner extension check

Author: jpolchlo

pystac/extensions/raster.py

@@ -729,6 +729,9 @@ def ext(cls, obj: T, add_if_missing: bool = False) -> RasterExtension[T]:
             cls.validate_owner_has_extension(obj, add_if_missing)
             return cast(RasterExtension[T], AssetRasterExtension(obj))
         elif isinstance(obj, item_assets.AssetDefinition):
+            cls.validate_has_extension(
+                cast(Union[pystac.Item, pystac.Collection], obj.owner), add_if_missing
+            )
             return cast(RasterExtension[T], ItemAssetsRasterExtension(obj))
         else:
             raise pystac.ExtensionTypeError(