Prevent undefined array key in asset observer

[marcusmoore]

This PR simply adds an array_key_exists to help prevent "undefined array key" exceptions.

I haven't tracked down exactly how this happens but adding an array_key_exists check should prevent the issue.

[what-the-diff]

PR Summary

• Improved Error Handling in AssetObserver
  The PR contains an update to the updating method in AssetObserver. Specifically, it now includes a condition to verify if an attribute exists before comparing its values. This enhancement prevents possible errors related to non-existent indexes, ultimately improving the robustness and reliability of the system.