Wordpress Customizer not Saving Data - wordpress-theming

Question

I have a function to add a option to the wordpress customiser, its uploading an image to a header as well as a control for changing the color. the problem im having is that while i can upload and preview a color or image, after refreshing the page the change is removed, so i assume its not saving correctly?
below is the code in the functions file.
// ADD HEADER IMAGE AND COLOR TO CUSTOMIZER
function customizer_header ( $wp_customize ) {
// ADD SECTIONS
$wp_customize->add_section( 'header_section', array(
'title' => __( 'Navigation Bar', 'dc_header' ),
'priority' => 80,
) );
// ADD SETTINGS
$wp_customize->add_setting( 'header_color',
array(
'default' => '',
'sanitize_callback' => '',
) );
$wp_customize->add_setting( 'header_image',
array(
'default' => '',
'sanitize_callback' => '',
) );
// ADD CONTROLS
$wp_customize->add_control(
new WP_Customize_Color_Control(
$wp_customize, 'header_color',
array(
'label' => __( 'Header Color' ),
'section' => 'header_section',
'settings' => 'header_color',
) ) );
$wp_customize->add_control(
new WP_Customize_Image_Control(
$wp_customize, 'header_image',
array(
'label' => __( 'Header Image', 'dc_header' ),
'section' => 'header_section',
'settings' => 'header_image',
) ) );
}
add_action( 'customize_register', 'customizer_header' );
I saw another post where someone was using this snippet, do i need to use this?
ive had it working without this in the past though but unsure whats the best way.
// ADD TO FRONTEND
function dc_header_frontend() {
?>
<style type="text/css">
#custom-header { background: <?php echo get_theme_mod( 'header_color' ); ?>; }
</style>
<?php
}

Answer 1

UPDATE: Found the problem to this, is was the allocated memory kept running out so upped the amount in the htaccess file, this has resolved the problem for anyone else experiencing it.