More fixes for invoice_to, fix PushNew on belongs to relations

app/Models/Invoice.php

@@ -24,6 +24,9 @@ class Invoice extends Model
 	protected $dates = ['date_orig','due_date'];
 	public $dateFormat = 'U';
 
+	// Array of items that can be updated with PushNew
+	protected $pushable = ['items'];
+
 	protected $appends = [
 		'date_due',
 		'due',