/**
 * Modify WP_Query to support 'meta_or_tax' argument
 * to use OR between meta- and taxonomy query parts.
 * use '_meta_or_tax' => true in wp_query array
 */
add_filter( 'posts_where', function( $where, WP_Query $q ){
	$tax_args = isset( $q->query_vars['tax_query'] ) ? $q->query_vars['tax_query'] : null;
	$meta_args = isset( $q->query_vars['meta_query'] ) ? $q->query_vars['meta_query'] : null;
	$meta_or_tax = isset( $q->query_vars['_meta_or_tax'] ) ? wp_validate_boolean( $q->query_vars['_meta_or_tax'] ) : false;
	// Construct the "tax OR meta" query
	if( $meta_or_tax && is_array( $tax_args ) &&  is_array( $meta_args )  )   {
		global $wpdb;
		$field = 'ID';// Primary id column
		$sql_tax = get_tax_sql(  $tax_args,  $wpdb->posts, $field );// Tax query
		$sql_meta = get_meta_sql( $meta_args, 'post', $wpdb->posts, $field );// Meta query
		// Modify the 'where' part
		if( isset( $sql_meta['where'] ) && isset( $sql_tax['where'] ) ) {
			$where = str_replace( [ $sql_meta['where'], $sql_tax['where'] ], '', $where );
			$where .= sprintf( ' AND ( %s OR  %s ) ', substr( trim( $sql_meta['where'] ), 4 ), substr( trim( $sql_tax['where']  ), 4 ) );
		}
	}
	return $where;
}, PHP_INT_MAX, 2 );

$args = array(
	'post_status'			=> 'publish',
	'order'					=> 'ASC',
	'nopaging'				=> true,
	'_meta_or_tax'			=> true, //用于支持 tax_query OR meta_query 查询
	'tax_query'				=> array(
		'relation'		=> 'OR',
		array(
			'taxonomy'	=> 'category',
			'field'		=> 'id',
			'terms'		=> array(1,2,3),
			'operator'	=> 'IN'
		), 
	),
	'meta_query'			=> array(
		array(
			'key'		=> 'Headline',
			'value'		=> ''
			'compare'	=> '!='
		),
	)
);
$query = new WP_Query( $args );