Prop Test

$meta_query = array(
	'relation' => 'OR',
	array(
		'key'     => 'prop_id',
		'value'   => 'array()',
		'compare' => '=',
	),
	array(
		'key'     => 'prop_id',
		'value'   => 'array()',
		'compare' => 'NOT IN',
	),
);