symfony- update entity and changed fields - php

Question

I try editAction in symfony but I have error when if not change input file it update field file in database to null ... how to not update field file if not changed value in update action
code action:
/**
* #Route("/babysitter/update/{id}", name="update_babysitter_by_admin")
*
* #param Request $request
* #param BabySitter $babySitter
* #ParamConverter("id", options={"id": "id"})
*
* #return mixed
*/
public function updateBabySitterAction(BabySitter $babySitter, Request $request){
$em= $this->getDoctrine()->getManager();
$form= $this->createForm(BabySitterType::class, $babySitter,['requiredFile'=> false]);
$form->handleRequest($request);
if($form->isSubmitted() && $form->isValid()){
if($babySitter->getPicture()->getDocument()){
$this->uploadDocument->upload($babySitter->getPicture(), $this->getParameter('pictures_directory'));
}
if($babySitter->getCriminalRecord()->getDocument()){
$this->uploadDocument->upload($babySitter->getCriminalRecord(), $this->getParameter('criminalRecord_director_babySitter'));
}
if($babySitter->getIdCards()){
$this->uploadDocument->uploadIdCard($babySitter->getIdCards(), $babySitter,$this->getParameter('idCard_directory'));
}
$em->persist($babySitter);
$em->flush();
$url = $this->generateUrl('info_babySitter',['id'=> $babySitter->getId()]);
$response = new RedirectResponse($url);
return $response;
}
return $this->render('admin/registerBabySitter.html.twig',[
'form'=> $form->createView()
]);
}
code twig:
{% trans_default_domain 'FOSUserBundle' %}
<div class="register-box" style="width:460px">
<div class="register-box-body">
<p class="login-box-msg">Register a new BabySitter</p>
{{ form_start(form, {'method':'post', 'attr': {'class': 'fos_user_registration_register', 'novalidate': 'novalidate'}}) }}
<div class="form-group has-feedback">
{{ form_widget(form.email,{'attr': {'class': 'form-control', 'placeholder': 'Email'}}) }}
{{ form_errors(form.email) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.firstName,{'attr': {'class': 'form-control', 'placeholder': 'FirstName'}}) }}
{{ form_errors(form.firstName) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.lastName,{'attr': {'class': 'form-control', 'placeholder': 'LastName'}}) }}
{{ form_errors(form.lastName) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.plainPassword.first,{'attr': {'class': 'form-control', 'placeholder': 'Password'}}) }}
{{ form_errors(form.plainPassword.first) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.plainPassword.second,{'attr': {'class': 'form-control', 'placeholder': 'Repeat Password'}}) }}
{{ form_errors(form.plainPassword.second) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.genre,{'attr': {'class': 'form-control', 'placeholder': 'Genre'}}) }}
{{ form_errors(form.genre) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.dateBirth,{'attr': {'class': 'form-control', 'placeholder': 'date Birthday'}}) }}
{{ form_errors(form.dateBirth) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.linkVideo,{'attr': {'class': 'form-control', 'placeholder': 'link Video'}}) }}
{{ form_errors(form.linkVideo) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.criminalRecord) }}
{{ form_errors(form.criminalRecord) }}
</div>
<div class="form-group has-feedback">
<ul id="idCard-fields-list"
data-prototype="{{ form_widget(form.idCards.vars.prototype)|e }}"
data-widget-tags="{{ '<li></li>'|e }}">
{{ form_row(form.idCards) }}
{% for idCardField in form.idCards %}
<li>
{{ form_errors(idCardField) }}
{{ form_widget(idCardField) }}
</li>
{% endfor %}
</ul>
<div class="row">
<button type="button"
class="add-another-collection-widget-idCard btn btn-primary btn-flat"
data-list="#idCard-fields-list">Add another idCard</button>
</div>
</div>
<div class="form-group has-feedback">
{{ form_widget(form.nbrYears,{'attr': {'class': 'form-control', 'placeholder': 'Number Years'}}) }}
{{ form_errors(form.nbrYears) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.rib,{'attr': {'class': 'form-control', 'placeholder': ' rib'}}) }}
{{ form_errors(form.rib) }}
</div>
<div class="form-group has-feedback">
{{ form_widget(form.presentation,{'attr': {'class': 'form-control', 'placeholder': 'presentation'}}) }}
{{ form_errors(form.presentation) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.adress) }}
{{ form_errors(form.adress) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.availability) }}
{{ form_errors(form.availability) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.assignement) }}
{{ form_errors(form.assignement) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.qualification) }}
{{ form_errors(form.qualification) }}
</div>
<div class="form-group has-feedback">
{{ form_row(form.picture) }}
{{ form_errors(form.picture) }}
</div>
<div class="form-group has-feedback">
<ul id="language-fields-list"
data-prototype="{{ form_widget(form.languages.vars.prototype)|e }}"
data-widget-tags="{{ '<li></li>'|e }}">
{{ form_widget(form.languages) }}
{% for languageField in form.languages %}
<li>
{{ form_errors(languageField) }}
{{ form_widget(languageField) }}
</li>
{% endfor %}
</ul>
<div class="row">
<button type="button"
class="add-another-collection-widget btn btn-primary btn-flat"
data-list="#language-fields-list">Add another language</button>
</div>
</div>
<div class="row">
<div class="col-xs-12">
<input type="submit" class="btn btn-primary btn-block btn-flat" value="{{ 'registration.submit'|trans }}">
</div>
<!-- /.col -->
</div>
{{ form_rest(form) }}
{{ form_end(form) }}
</div>
<!-- /.form-box -->
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
jQuery(document).ready(function () {
jQuery('.add-another-collection-widget').click(function (e) {
var list = jQuery(jQuery(this).attr('data-list'));
// Try to find the counter of the list or use the length of the list
var counter = list.data('widget-counter') | list.children().length;
// grab the prototype template
var newWidget = list.attr('data-prototype');
// replace the "__name__" used in the id and name of the prototype
// with a number that's unique to your emails
// end name attribute looks like name="contact[emails][2]"
newWidget = newWidget.replace(/__name__/g, counter);
// Increase the counter
counter++;
// And store it, the length cannot be used if deleting widgets is allowed
list.data('widget-counter', counter);
// create a new list element and add it to the list
var newElem = jQuery(list.attr('data-widget-tags')).html(newWidget);
newElem.appendTo(list);
addTagFormDeleteLink(newElem);
});
function addTagFormDeleteLink($tagFormLi) {
var $removeFormButton = $('<button class="btn btn-danger btn-flat" style="margin-top:2%;margin-left:50%" type="button">Delete this Language</button>');
$tagFormLi.append($removeFormButton);
$removeFormButton.on('click', function(e) {
// remove the li for the tag form
$tagFormLi.remove();
});
}
jQuery('.add-another-collection-widget-idCard').click(function (e) {
var list = jQuery(jQuery(this).attr('data-list'));
// Try to find the counter of the list or use the length of the list
var counter = list.data('widget-counter') | list.children().length;
// grab the prototype template
var newWidget = list.attr('data-prototype');
// replace the "__name__" used in the id and name of the prototype
// with a number that's unique to your emails
// end name attribute looks like name="contact[emails][2]"
newWidget = newWidget.replace(/__name__/g, counter);
// Increase the counter
counter++;
// And store it, the length cannot be used if deleting widgets is allowed
list.data('widget-counter', counter);
// create a new list element and add it to the list
var newElem = jQuery(list.attr('data-widget-tags')).html(newWidget);
if(counter <= 3){ newElem.appendTo(list); }
});
function addIdCardFormDeleteLink($tagFormLi) {
var $removeFormButton = $('<button class="btn btn-danger btn-flat" style="margin-top:2%;margin-left:50%" type="button">Delete this idCard</button>');
$tagFormLi.append($removeFormButton);
$removeFormButton.on('click', function(e) {
// remove the li for the tag form
$tagFormLi.remove();
});
}
});
</script>
when i update entity and i not update field file i have field file in database null ... how to update entity without changed in input file