Error: Undefined index on admin.php (fix)

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ERROR
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Notice: Undefined index: music_album in <b>D:\HTTP\www\wp-content\plugins\custompress\core\admin.php on line 44

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ORIGINAL
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if ( isset( $_GET['post_type'] ) && true === is_array( $this->post_types[$_GET['post_type']] ) ) {
add_filter( 'manage_edit-' . $_GET['post_type'] . '_columns', array( &$this, 'add_new_cf_columns' ) );
add_action( 'manage_' . $_GET['post_type'] . '_posts_custom_column', array( &$this, 'manage_cf_columns' ), 10, 2 );
}

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FIX
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if (isset($_GET['post_type']))
{
$this->post_types[] = $_GET['post_type'];
if (is_array($this->post_types) === true) {
add_filter( 'manage_edit-' . $_GET['post_type'] . '_columns', array( &$this, 'add_new_cf_columns' ) );
add_action( 'manage_' . $_GET['post_type'] . '_posts_custom_column', array( &$this, 'manage_cf_columns' ), 10, 2 );
}
}