Icon picker fatal error

Comienza en includes/fields/class-acf-field-icon_picker.php, línea 132, y reproduce el fallo con la pestaña personalizada y los filtros de iconos mostrados en el issue. Usa la configuración de bloque de ACF proporcionada y las versiones de WordPress/PHP para confirmar la ruta de renderizado que falla. Se considera terminado cuando el editor de páginas carga el bloque con el conjunto de iconos personalizado sin un error fatal.

Describe the bug
When using the icon picker field type in a custom ACF block with a custom icon set I am getting the following error when trying to edit a page where that block is used:

Fatal error: Uncaught TypeError: Cannot access offset of type string on string in /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/fields/class-acf-field-icon_picker.php:132 Stack trace: #0 /var/www/html/wp-includes/class-wp-hook.php(324): acf_field_icon_picker->render_field(Array) #1 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array) #2 /var/www/html/wp-includes/plugin.php(565): WP_Hook->do_action(Array) #3 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-hook-functions.php(113): do_action_ref_array('acf/render_fiel...', Array) #4 /var/www/html/wp-includes/class-wp-hook.php(324): _acf_apply_hook_variations(Array) #5 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array) #6 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #7 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-field-functions.php(807): do_action('acf/render_fiel...', Array) #8 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-field-functions.php(763): acf_render_field(Array) #9 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-field-functions.php(614): acf_render_field_wrap(Array, 'div', 'field') #10 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/pro/blocks.php(613): acf_render_fields(Array, 'block_32caf81ff...', 'div', 'field') #11 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/pro/blocks.php(543): acf_rendered_block(Array, '', true, 1307, Object(WP_Block)) #12 /var/www/html/wp-includes/class-wp-block.php(586): acf_render_block_callback(Array, '', Object(WP_Block)) #13 /var/www/html/wp-includes/blocks.php(2358): WP_Block->render() #14 /var/www/html/wp-includes/blocks.php(2410): render_block(Array) #15 /var/www/html/wp-includes/class-wp-hook.php(324): do_blocks('<!-- wp:acf/her...') #16 /var/www/html/wp-includes/plugin.php(205): WP_Hook->apply_filters('<!-- wp:acf/her...', Array) #17 /var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php(1961): apply_filters('the_content', '<!-- wp:acf/her...') #18 /var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php(655): WP_REST_Posts_Controller->prepare_item_for_response(Object(WP_Post), Object(WP_REST_Request)) #19 /var/www/html/wp-includes/rest-api/class-wp-rest-server.php(1292): WP_REST_Posts_Controller->get_item(Object(WP_REST_Request)) #20 /var/www/html/wp-includes/rest-api/class-wp-rest-server.php(1125): WP_REST_Server->respond_to_request(Object(WP_REST_Request), '/wp/v2/pages/(?...', Array, NULL) #21 /var/www/html/wp-includes/rest-api.php(586): WP_REST_Server->dispatch(Object(WP_REST_Request)) #22 /var/www/html/wp-includes/rest-api.php(2973): rest_do_request(Object(WP_REST_Request)) #23 [internal function]: rest_preload_api_request(Array, '/wp/v2/pages/13...') #24 /var/www/html/wp-includes/block-editor.php(754): array_reduce(Array, 'rest_preload_ap...', Array) #25 /var/www/html/wp-admin/edit-form-blocks.php(114): block_editor_rest_api_preload(Array, Object(WP_Block_Editor_Context)) #26 /var/www/html/wp-admin/post.php(187): require('/var/www/html/w...') #27 {main} thrown in /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/fields/class-acf-field-icon_picker.php on line 132

To Reproduce
Steps to reproduce the behavior:

1. Create an ACF block with an icon picker field with a custom icon set.
2. Use the following code (or similar) in functions.php to manage the custom icon set

add_filter('acf/fields/icon_picker/tabs', function(array $tabs): array {
    $tabs['nwlp'] = 'NWLP';
    return $tabs;
});

add_filter('acf/fields/icon_picker/nwlp/icons', function(array $icons): array {
    $base_url = get_template_directory_uri() . '/assets/images/icons/';

    return [
        [
            'url'   => $base_url . 'accreditations.svg',
            'key'   => 'accreditations',
            'label' => 'Accreditations',
        ],
        [
            'url'   => $base_url . 'audio-podcast.svg',
            'key'   => 'audio-podcast',
            'label' => 'Audio podcast',
        ]
    ];
});

3. Try to insert/edit a page where this block is embedded and the error should show.

Expected behavior
No error to show

Code

{
    "key": "group_687639d742f8f",
    "title": "Block: Icon",
    "fields": [
        {
            "key": "field_687639d70f893",
            "label": "Icon",
            "name": "icon",
            "aria-label": "",
            "type": "icon_picker",
            "instructions": "",
            "required": 0,
            "conditional_logic": 0,
            "wrapper": {
                "width": "",
                "class": "",
                "id": ""
            },
            "tabs": [
                "nwlp"
            ],
            "return_format": "array",
            "allow_in_bindings": 0,
            "library": "all",
            "default_value": {
                "type": null,
                "value": null
            }
        },
        {
            "key": "field_68763a145e4e2",
            "label": "Icon Colour",
            "name": "icon_colour",
            "aria-label": "",
            "type": "select",
            "instructions": "",
            "required": 0,
            "conditional_logic": 0,
            "wrapper": {
                "width": "",
                "class": "",
                "id": ""
            },
            "choices": {
                "blue": "Blue",
                "green": "Green",
                "pink": "Pink"
            },
            "default_value": false,
            "return_format": "value",
            "multiple": 0,
            "allow_null": 0,
            "allow_in_bindings": 0,
            "ui": 0,
            "ajax": 0,
            "placeholder": "",
            "create_options": 0,
            "save_options": 0
        }
    ],
    "location": [
        [
            {
                "param": "block",
                "operator": "==",
                "value": "acf\/icon"
            }
        ]
    ],
    "menu_order": 0,
    "position": "normal",
    "style": "default",
    "label_placement": "top",
    "instruction_placement": "label",
    "hide_on_screen": "",
    "active": true,
    "description": "",
    "show_in_rest": 0,
    "modified": 1752583984
}

Version Information:

• WordPress Version 6.8.2
• PHP Version 8.2.28
• ACF Version ACF Pro 6.4.3
• Browser Chrome 138