Illegal string offset in PHP function in via Theme Customizer

I have this setting in wp_customize:

        // Select share box options.
    $wp_customize-add_setting( 'single_share_box_options',
    array(
        'default' = $this-defaults['single_share_box_options'],
        'transport' = 'refresh',
        'sanitize_callback' = 'quanticthemes_text_sanitization',
        'active_callback' = 'quanticthemes_share_box_condition',
    )
    );
    $wp_customize-add_control( new Customizer_Simple_Checkbox_Control( $wp_customize, 'single_share_box_options',
    array(
        'label' = __( 'Share Box Options', 'custom' ),
        'description' = esc_html__( 'Select share box options.', 'custom' ),
        'section' = 'single_post_general_section',
        'active_callback' = 'quanticthemes_share_box_condition',
        'input_attrs' = array(
            'sortable' = false,
            'fullwidth' = true,
        ),
        'choices' = array(
            'facebook' = esc_html__('Facebook', 'custom'),
            'twitter' = esc_html__('Twitter', 'custom'),
            'linkedin' = esc_html__('Linkedin', 'custom'),
            'pinterest' = esc_html__('Pinterest', 'custom'),
            'telegram' = esc_html__('Telegram', 'custom'),
            'email' = esc_html__('Email', 'custom'),
            'whatsapp' = esc_html__('WhatsApp', 'custom'),
            'link' = esc_html__('Link Box', 'custom'),
        ),
    )
    ) );

Then I try to output like this:

        $social = CustomTheme::$options['single_share_box_options'];
        ?php if( $social['facebook'] ): ?
        divMy content/div
        ?php endif; ?
        ?php if( $social['twitter'] ): ?
        divMy content/div
        ?php endif; ?

But I get Warning: Illegal string offset 'facebook' .... Any help please?