Display assigned terms with link

Keep in mind that the return value of get_the_terms() can be of the type of

array|WP_Error

Your snippet should check if you get the correct type returned

$terms = get_the_terms( 0, 'product_tag' );
if (
    ! is_wp_error( $terms )
    AND is_array( $terms )
    AND ! empty( $terms )
    )
{
    foreach( $terms as $term )
        printf(
            '<a href="https://wordpress.stackexchange.com/questions/163332/%s" style="font-size: 8pt; margin-right:5px;">%s</a>',
            esc_url( get_term_link( $term ) ),
            $term
        );
}