I am using the Apex for Xero package from Ben Edwards on GitHub and I am trying to populate a Xero contact record with a Xero Address (which is a nested list) and I'm getting FATAL_ERROR System.NullPointerException: Attempt to de-reference a null object.

Looking at other questions on this subject it seems to relate to not initialising things, but I believe I am initialising everything.

Does anyone have any pointers for me? 

Thanks

Barry

global class SFtoXero {

/* XeroContact Structure
 * <Contacts>
   <Contact>
     <ContactID>bd2270c3-8706-4c11-9cfb-000b551c3f51</ContactID>
     <ContactStatus>ACTIVE</ContactStatus>
     <Name>ABC Limited</Name>
     <FirstName>Andrea</FirstName>
     <LastName>Dutchess</LastName>
     <EmailAddress>a.dutchess@abclimited.com</EmailAddress>
     <SkypeUserName>skype.dutchess@abclimited.com</SkypeUserName>
     <BankAccountDetails>45465844</BankAccountDetails>
     <TaxNumber>415465456454</TaxNumber>
     <AccountsReceivableTaxType>INPUT2</AccountsReceivableTaxType>
     <AccountsPayableTaxType>OUTPUT2</AccountsPayableTaxType>
     <Addresses>
       <Address>
         <AddressType>POBOX</AddressType>
         <AddressLine1>P O Box 123</AddressLine1>
         <City>Wellington</City>
         <PostalCode>6011</PostalCode>
         <AttentionTo>Andrea</AttentionTo>
       </Address>
       <Address>
         <AddressType>STREET</AddressType>
       </Address>
     </Addresses>
     <Phones>
       <Phone>
         <PhoneType>DEFAULT</PhoneType>
         <PhoneNumber>1111111</PhoneNumber>
         <PhoneAreaCode>04</PhoneAreaCode>
         <PhoneCountryCode>64</PhoneCountryCode>
       </Phone>
       <Phone>
         <PhoneType>FAX</PhoneType>
       </Phone>
       <Phone>
         <PhoneType>MOBILE</PhoneType>
       </Phone>
       <Phone>
         <PhoneType>DDI</PhoneType>
       </Phone>
     </Phones>
     <UpdatedDateUTC>2009-05-14T01:44:26.747</UpdatedDateUTC>
     <IsSupplier>false</IsSupplier>
     <IsCustomer>true</IsCustomer>
     <DefaultCurrency>NZD</DefaultCurrency>
   </Contact>
 </Contacts>
         
*/         
    global class contactRecord {
        @invocableVariable global string PracticeName;
        @invocableVariable global string PartnerFirstName;
        @invocableVariable global string PartnerLastName;
        @invocableVariable global string EmailAddress;
        @invocableVariable global string AddressLine1;
        @invocableVariable global string City;
        @invocableVariable global string PostalCode;
        @invocableVariable global string AccountID;
    }
    
    
    @InvocableMethod(label='Create a Contact In Xero' description='Creates a Xero Contact Record')

    global static void createContact(List<contactRecord> XeroContacts) {
        
        for(contactRecord c: XeroContacts) {
            
       		calloutMethod(c.PracticeName, c.PartnerFirstName, c.PartnerLastName, c.emailAddress, c.city, c.AccountID);
    	}
    
    }
    
    @future(callout=true)

    public static void calloutmethod(	string practiceName, 
                                     	string partnerFirstname, 
                                     	string partnerLastname,
                                    	string emailAddress,
                                    	string City,
                                    	String AccountID){

        // Create a Contact
        // 

            XeroAddress addr = new XeroAddress();
            
            addr.AddressType ='x';
            addr.AddressLine1 = 'x';
            addr.AddressLine2 ='x';
            addr.AddressLine3 = 'x';
            addr.AddressLine4 = 'x';
            addr.City = City;
            addr.Region = 'x';                               
			addr.PostalCode = 'x';
            addr.Country = 'x';
            addr.AttentionTo = 'x';
                                            
            XeroContact newContact = new XeroContact();
                                            
            newContact.Name = practiceName;
            newContact.FirstName = partnerFirstname;
            newContact.LastName = partnerLastname;
            newContact.EmailAddress = emailAddress;
            newContact.Addresses.add(addr);                                
            
        
        // Send Contact to Xero
            try {
            	XeroContact createdContact=XeroAccountingApi.createContact(XeroXmlUtility.serialize(newContact, 'Contact'));
                system.debug('Created Contact ID: '+createdContact.ContactID);
                Xero_contact__c XeroContactinSF = new Xero_Contact__c();
                XeroContactinSF.Xero_Contact_ID__c = createdContact.ContactID;
                XeroContactinSF.Name = createdContact.Name;
                XeroContactinSF.Account__c = AccountID;
                
                insert XeroContactinSF;
			} catch (Exception ex){
            	system.debug(ex);
        	}	     
    }
    
}