Deprecated functionality: strlen(): Passing null to parameter #1

I am getting this error with PHP 8.3 in the system.log file:

```Deprecated functionality: strlen(): Passing null to parameter #1 ($string) of type string is deprecated  in /var/www/html/app/code/core/Mage/Wishlist/Controller/Abstract.php on line 88```

**/app/code/core/Mage/Wishlist/Controller/Abstract.php on line 88**

In order to reproduce this issue log into a customer account in the Frontend then add any product to the Wishlist. You will be redirected to the customer account. A part of the URL is **wishlist/index/index/wishlist_id/[PRODUCT_ID]/**. Press the [Add All to the Cart] button. In my case I am getting an error message because the product has custom options and I have to choose them. If you take a look into the /var/log directory you will see a nice system.log file, having 374 kB as size and inside the same line 1745 times.

IMPORTANT NOTE: 
This PR has 3 implementations inside (3 lines, 2 commented), there may be others. Please share your opinions, at the end there will be only one line left.

app/code/core/Mage/Wishlist/Controller/Abstract.php

@@ -85,7 +85,9 @@ public function allcartAction()
 
         $qtysString = $this->getRequest()->getParam('qty');
         if (isset($qtysString)) {
-            $qtys = array_filter(json_decode($qtysString), '\strlen');
+            $qtys = array_filter(json_decode($qtysString), fn($qtysString) => strlen($qtysString ?? ''));
+            // $qtys = array_filter(json_decode($qtysString), function ($qtysString) { return strlen($qtysString ?? ''); });
+            // $qtys = @array_filter(json_decode($qtysString), '\strlen');
         }
 
         /** @var Mage_Wishlist_Model_Item $item */