$post global object

[Amer-Moh]

Hi, I'm trying to use your method to build OOP theme from scratch, everything was good till I got this error:
https://i.imgur.com/Kk1fIV4.png when I tried to use block_categories like this https://i.imgur.com/Yohaw00.png :

public function my_block_category( $categories , $post ) {        
    return array_merge(
        $categories,
        array(
            array(
                'slug' => 'trc-blocks',
                'title' => __( 'Site Blocks', 'trc-blocks' ),
            ),
        )
    );
}

Can you help me please?

[Amer-Moh]

Fixed, it was related to the action priority