Two collection on zul page returning null when both of them becomes empty.

		<!-- insert contact info here -->
			<groupbox>
				<caption label="Contact Information" ></caption>
				<listbox id="clist" model="@load(vm.clientContacts) @save(vm.client.clientContacts)">
					<listhead>
				        <listheader label=""></listheader>
				        <listheader label="" width="30px"></listheader>
				    </listhead>
					<template name="model" var="contact">
					<listitem>
						<listcell hflex="1">
							<n:table width="100%" cellspacing="5" border="0">
							<n:tr>
							<n:td>
								Title<n:br></n:br>
								<combobox model="@bind(vm.salutationList)" width="70px" selectedItem="@bind(contact.salutation)">
									<template name="model" var="title">
										<comboitem label="@bind(title)"></comboitem>
									</template>
								</combobox>
							</n:td>
							<n:td>
							<!-- constraint="/.+@.+\.+/: Invalid e-mail address" remove for now -->
							Name<n:br></n:br><textbox value="@bind(contact.name)" width="90%"></textbox>
							</n:td>
							<n:td>
							Telephone<n:br></n:br><textbox value="@bind(contact.phone)"></textbox>
							</n:td>
							<n:td>
							Mobile<n:br></n:br><textbox value="@bind(contact.mobile)" ></textbox>
							</n:td>
							<n:td>
							Fax<n:br></n:br><textbox value="@bind(contact.fax)" ></textbox>
							</n:td>
							</n:tr>
							<n:tr>							
							<n:td>
							Email<n:br></n:br><textbox value="@bind(contact.email)" width="90%"></textbox>
							</n:td>
							<n:td>
							MSN ID<n:br></n:br><textbox value="@bind(contact.msnId)"></textbox>
							</n:td>
							<n:td>
							Skype ID<n:br></n:br><textbox value="@bind(contact.skypeId)"></textbox>
							</n:td>
							<n:td colspan="3">
							Remarks<n:br></n:br><textbox width="70%" value="@bind(contact.remarks)"></textbox>
							</n:td></n:tr>
							</n:table>
						</listcell>
						<listcell>
						<hlayout><image src="/resources/images/cancel.png" onClick="@command('removeContact', index=clist.getSelectedIndex(), comp=savebtn)" ></image></hlayout>
						</listcell>
					</listitem>
					</template>
					<listfoot>
		            <listfooter id="footerContact" span="8" align="right"><button onClick="@command('addMoreContact')" label="add more contact"></button></listfooter>
       				</listfoot>	
				</listbox>			
			</groupbox>
			<!--  insert bank info here -->	
			<groupbox>
				<caption label="Bank Information"></caption>
				<listbox id="bankList" model="@load(vm.bankInfos) @save(vm.client.bankinfos)">
					<listhead>
				        <listheader label=""></listheader>
				        <listheader label="" width="30px"></listheader>
				    </listhead>
					<template name="model" var="bankInfo">
					<listitem>
						<listcell>
							<n:table width="100%" cellspacing="5" border="0">
							<n:tr>
							<n:td>Bank Client Name<n:br></n:br><textbox value="@bind(bankInfo.bankClientName)" width="90%"></textbox></n:td>
							<n:td>Bank Type<n:br></n:br>
								<combobox readonly="true" model="@bind(vm.bankType)" selectedItem="@bind(bankInfo.bankType)">
									<template name="model" var="item">
									<comboitem label="@bind(item)"></comboitem>
									</template>
								</combobox>
							</n:td>
							<n:td>Bank Name<n:br></n:br><textbox value="@bind(bankInfo.bankName)" width="90%"></textbox></n:td>
							<n:td>Bank Address<n:br></n:br><textbox value="@bind(bankInfo.bankAddress)" width="90%"></textbox></n:td>
							<n:td>Account Number<n:br></n:br><textbox value="@bind(bankInfo.accountNumber)" width="90%"></textbox></n:td>
							</n:tr>
							<n:tr>
							<n:td>Swift Code<n:br></n:br><textbox value="@bind(bankInfo.swiftCode)"></textbox></n:td>
							<n:td>Iban<n:br></n:br><textbox value="@bind(bankInfo.iban)"></textbox></n:td>
							<n:td>Reference<n:br></n:br><textbox value="@bind(bankInfo.reference)"></textbox></n:td>
							<n:td>Remarks<n:br></n:br><textbox value="@bind(bankInfo.remarks)" width="90%"></textbox></n:td>
							</n:tr>
							</n:table>						
						</listcell>
						<listcell>
						<hlayout><image src="/resources/images/cancel.png" onClick="@command('removeBankInfos', index=bankList.getSelectedIndex(), comp=savebtn)" ></image></hlayout>
						</listcell>						
					</listitem>
					</template>
					<listfoot>
		            <listfooter id="footerBankInfos" span="8" align="right"><button onClick="@command('addMoreBankInfos')" label="add more bank information"></button></listfooter>
       				</listfoot>						
				</listbox>
			</groupbox>"]			

List<ClientContact> clientContacts = new ArrayList<ClientContact>();
List<BankInformation> bankInfos = new ArrayList<BankInformation>();

    @Command @NotifyChange("clientContacts")
    public void addMoreContact(){
    	clientContacts.add(new ClientContact());
    }

    @Command @NotifyChange("bankInfos")
    public void addMoreBankInfos(){
    	bankInfos.add(new BankInformation());
    }
    
    @Command @NotifyChange("clientContacts")
    public void removeContact(@BindingParam("index") int index, @BindingParam("comp") Component comp){
    	clientContacts.remove(index);
    	client.getClientContacts().clear();
    	client.getClientContacts().addAll(clientContacts);
	    Clients.showNotification("Click save to permanently delete this contact","warning", comp, "end_center",2000);
    }
    
    @Command @NotifyChange("bankInfos")
    public void removeBankInfos(@BindingParam("index") int index, @BindingParam("comp") Component comp){
    	bankInfos.remove(index);
    	client.getBankinfos().clear();
    	client.getBankinfos().addAll(bankInfos);
	    Clients.showNotification("Click save to permanently delete this bank information","warning", comp, "end_center",2000);
    }