PHP 8.5: Fix an invalid null array key in PHUIObjectItemListExample
Summary:
Per https://www.php.net/manual/en/language.types.array.php, regarding array key casts, "Null will be cast to the empty string".
Setting null as an array key is deprecated since PHP 8.5 per https://www.php.net/releases/8.5/en.php: "Using null as an array offset or when calling array_key_exists() is now deprecated. Use an empty string instead."
Test Plan: Go to "Color Icons" on http://phorge.localhost/uiexample/view/PHUIObjectItemListExample/ and look at the first bell icon and its HTML.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26510