How to set null value selectone menu jsf - primefaces

Question

I am using PrimeFaces 5.1 , I have a field Cumulative indicator which is a select drop down wit Y/N/select, when I update the value to Y/N the edit/update is happening fine, but when I chose select as the drop down value it does not update it to null. I am able to set the value to null from the backend. When I chose select as the drop down value it should update to null instead it shows the previous value(Y/N) that is saved in the database. The below is my code xhtml, java bean and the update query. Please advice why its not updating the value to null value.
I tried putting the drop down value itemValue="#{null}" but that didn't work as mentioned in this post How to save Null value with selectone dropdown
Below is my xhtml:
<p:column headerText="Cumulative Indicator" width="60">
<p:cellEditor>
<f:facet name="output">
<h:outputText value="#
{AcctRefRecord.cumIndicator}" />
</f:facet>
<f:facet name="input">
<h:selectOneMenu value="#{AcctRefRecord.cumIndicator}"
label="Cumulative Indicator">
<f:selectItem
itemLabel="--Select--" itemValue="" />
<f:selectItem
itemValue="Y" />
<f:selectItem
itemValue="N" />
</h:selectOneMenu>
</f:facet>
</p:cellEditor>
</p:column>
<p:dataTable id="dtable" var="AcctRefRecord"value="#
{AcctRefMBean.
AcctRefRecords}" editable="true"
paginator="true" rows="10"
paginatorTemplate="{CurrentPageReport} {FirstPageLink}
{PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink}
{RowsPerPageDropdown}" >
<p:ajax event="rowEdit" listener="#
{AcctRefMBean.onRowEdit}" update=":dtableform:msgs" resetValues="true"/>
<p:ajax event="rowEditCancel" listener="#
{AcctRefMBean.onRowCancel}" update=":dtableform:msgs"/>
Below is my javaBean:
//retrive the record/row of type
AcctRefTo on which edit even occurred
AcctRefTo to = (AcctRefTo)
event.getObject();
FacesContext facesContext = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession)
facesContext.getExternalContext().getSession(false);
String userId = (String)
session.getAttribute(WebAppConstants.CURRENT_USER_ID);
if (userId == null) {
userId = WebAppConstants.DEFAULT_CURRENT_USER_ID;
}
to.setUpdatedByUserID(userId);
updateRecord(to);
FacesMessage msg = new FacesMessage("Reference Data Updated for Account#"
+ to.getAcctNbr());
FacesContext.getCurrentInstance
().addMessage("null", msg);
}
/**
* #param to
* updates the given to in DB accordingly
*/
public void updateRecord(AcctRefTo to) {
jetSessionFacadebean.updateAccntRef(to);
}
Below is my updateQuery:
<key><value>updateAcctgRef</value></key>
<value>
update acct_ref set
cd_val=?,
dt_eff_end=?,
ind_bal=?,
ind_bal_acct_type=?,
ind_cum=?,
ind_net=?,
ind_net__bal_type=?,
ind__rcn=?,
ind_b=?,
nbr_gl_acct_yeb_offst=?,
nbr_gl_acct_net_unam_bal=?,
cd_fee_cat_type=?,
id_lst_updt=?,