php doctrine orm cant insert joinColumn null - php

Question

first at all thanks for reading.
I'm a little bit new with Doctrine Orm. My problem is that i have declared a class that has two oneToMany joinColumns, but i need to insert data even when i do not have those joinColumn data.
So, i have a var with three possible values, "factura" | "nota credito" | "nota debito". When "factura" is choosen then i have to add two arrayCollection() to add possible data. But when "nota credito" or "nota debito" choosen i dont have to add the arrays, but when that happends... the new factura object did not insert.
So here is my code of the Librarie and modelCode. Please see just the _construct and the last two joinColumns mapped.
public function insertaFactura($information) {
$cliente = $this->getCollectionByid("Cliente", $information['cob_cliente']);
$factura = new Factura($information, $cliente);
$this->orm->flush();
$this->orm->persist($factura);
if ($information['doc_tipo'] == "factura") {
if ($information['articulos']) {
foreach ($information['articulos'] as $key_venta => $articulos) {
foreach ($articulos as $articulo) {
$ventaArticulo = $this->getCollectionByid("Venta_Articulo", $articulo);
$fva = new Factura_Venta_Articulo();
$fva->setVentaArticulo($ventaArticulo);
$fva->setFactura($factura);
$this->orm->persist($fva);
}
}
$this->orm->flush();
}
}
return $factura->getId();
}
<?php
use \Doctrine\Common\Collections\ArrayCollection;
/**
* Factura
*
* #Table(name="documento_cliente")
* #Entity
*/
class Factura {
/**
* #var integer $id
*
* #Column(name="doc_id", type="integer", nullable=false)
* #Id
* #GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #var string $numero
*
* #Column(name="doc_numero", type="string", length=120, nullable=true)
*/
private $numero;
/**
* #var string $tipo
*
* #Column(name="doc_tipo", type="string")
*/
private $tipo;
/**
* #var string $fecha
*
* #Column(name="doc_fecha", type="date", length=1, nullable=true)
*/
private $fecha;
/**
* #var integer $estado
*
* #Column(name="doc_estado", type="integer", length=120, nullable=true)
*/
private $estado;
/**
* #OneToOne(targetEntity="Cliente", cascade={"persist", "remove"}))
* #JoinColumn(name="doc_cliente_id", referencedColumnName="cli_id")
* */
private $cliente;
/**
* #OneToMany(targetEntity="Factura_Venta_Articulo", mappedBy="factura")
* #JoinColumn(name="fva_ver_id", referencedColumnName="ver_id",nullable=true)
* */
private $venta_articulo;
/**
* #OneToMany(targetEntity="Cobro_factura", mappedBy="factura")
* #JoinColumn(name="cof_id", referencedColumnName="cobro_id",nullable=true)
* */
private $cobros;
public function getId() {
return $this->id;
}
public function getTipo() {
return $this->tipo;
}
public function getNumero() {
return $this->numero;
}
public function getFecha() {
return $this->fecha;
}
public function getEstado() {
return $this->estado;
}
public function getCliente() {
return $this->cliente;
}
public function getVentasArticulo() {
return $this->venta_articulo;
}
public function getCobros() {
return $this->cobros;
}
public function setNumero($numero) {
$this->numero = $numero;
}
public function setTipo($tipo) {
$this->tipo = $tipo;
}
public function setFecha($fecha) {
$this->fecha = $fecha;
}
public function setEstado($estado) {
$this->estado = $estado;
}
public function setCliente($cliente) {
$this->cliente = $cliente;
}
public function __construct($parameters, $cliente) {
$this->setEstado(3);
$this->setFecha(new \DateTime($parameters['factura_fecha']));
$this->setNumero($parameters['factura_numero']);
$this->setCliente($cliente);
$this->setTipo($parameters['doc_tipo']);
if ($parameters['doc_tipo'] == 'factura') {
$this->venta_articulo = new ArrayCollection();
$this->cobros = new ArrayCollection();
}
}
public function actualizar($numero, $fecha, $cliente) {
$this->setNumero($numero);
$this->setFecha(new \DateTime($fecha));
$this->setCliente($cliente);
}
public function totalFactura() {
$total = 0.0;
foreach ($this->venta_articulo as $ventaArticulo) {
$total+=$ventaArticulo->getVentaArticulo()->getIngreso();
}
return $total;
}
public function totalFacturaCobrado() {
$total = 0;
foreach ($this->cobros as $cobro) {
$total+=$cobro->getCobranza();
}
return number_format($total, 2, '.', '');
}
public function totalFacturaACobrar() {
return number_format($this->totalFactura(), 2, '.', '') - number_format($this->totalFacturaCobrado(), 2, '.', '');
}
}