Fix(Core): Fix json_decode for 'itemtypes' field

[stonebuzz]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
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Description

Fix :

• Plugin does not activate #1034
• An error occurred when deleting an asset (in particular a computer) #1022

Prevent error when decoding itemtypes with GLPI custom asset classes

[2025-10-24 07:35:00] glpi.CRITICAL: *** Uncaught PHP Exception Twig\Error\RuntimeError: 
"An exception has been thrown during the rendering of a template 
("in_array(): Argument #2 ($haystack) must be of type array, null given") 
in "pages/generic_form.html.twig" at line 33." 
at generic_form.html.twig line 33
Backtrace :

The issue occurs when fields['itemtypes'] contains GLPI Custom Asset class names using namespaces, for example:

["Ticket", "Glpi\CustomAsset\Car"]

In such cases, json_decode() fails because unescaped backslashes make the JSON string invalid, returning null instead of an array.

To ensure consistent decoding of itemtypes, enforce the use of the following helper method:

public static function decodeJSONItemtypes(string $itemtypes, ?bool $associative = null)
{
    $jsonitemtype = json_decode($itemtypes, $associative);

    // Attempt recovery when JSON decoding fails due to unescaped backslashes
    if ($jsonitemtype === null && json_last_error() !== JSON_ERROR_NONE) {
        $fixed_json = str_replace('\\', '\\\\', $itemtypes);
        $jsonitemtype = json_decode($fixed_json, $associative);
    }

    return $jsonitemtype;
}

This ensures proper decoding of itemtypes even when they contain GLPI namespaced asset classes, avoiding in_array() runtime errors during template rendering.

Fix migration for GenericObject itemtypes

The migration process for GenericObject types has been updated to correctly generate the corresponding GLPI Custom Asset class names using proper namespace escaping:

foreach ($result as $type) {
    $migration_genericobject_itemtype[$type['itemtype']] = [
        'genericobject_itemtype' => $type['itemtype'],
        'itemtype' => 'Glpi\\\\CustomAsset\\\\' . $type['name'] . 'Asset', // HERE
        'genericobject_name' => $type['name'],
        'name' => $type['name'] . 'Asset',
    ];
}

This ensures that migrated itemtypes reference the correct fully qualified class names (e.g., Glpi\\CustomAsset\\Car) and remain compatible with json_decode() and Twig rendering.

For instances that have already completed the migration prior to this fix, the correction must still be applied to maintain consistency and prevent runtime errors during template rendering.