PHP warning if extension not present - optimized_assets_proxy_restore_file

Problem/Motivation

Error message:
Undefined array key "extension" in optimized_assets_proxy_restore_file called at /code/web/modules/contrib/optimized_assets_proxy/src/EventSubscriber/MissingAsset.php (74)
 /in Drupal\optimized_assets_proxy\EventSubscriber\MissingAsset::findAndWrite called at ? (?)
in call_user_func called at /code/web/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php (111)

Steps to reproduce

Example path to handle: /sites/default/files/js/js_eUgcD6GynsW5mLBvwPcF5-tqpeP8MHTTiUvBVEW3LvU.js%22

Proposed resolution

Check if the "extension" key is present.

Remaining tasks

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User interface changes

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API changes

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Data model changes