Wordpress unknown database error with select

This is code from child functions.php:

function f_goscie(){
    global $wpdb;
    $kateg = $wpdb->get_results( 'SELECT * FROM kategorie');
}

add_shortcode('goscie','f_goscie');

And this is code from my plugin:

function dominik_play(){
    global $wpdb;
    define( 'DIEONDBERROR', true ); //i have multisite on
    $wpdb->show_errors();

    $kateg = $wpdb->get_results( 'SELECT * FROM kategorie');
    $wpdb->print_error();
}

add_shortcode('ytplejer','dominik_play');

The first code works without any problems. It's part of bigger code which gets data from my own tables
http://niezaleznylublin.pl/nasi-goscie/

The second code throws this error:

Wordpress database error: [] SELECT * FROM kategorie

niezaleznylublin.pl/player

I dont have ANY ideas why those two very similar functions give different results and one is error.