Apex Class Extension: Updating related field using standard controller - class

Question

I am relatively new to Apex:
Im trying to save a related field via my visualforce page, the apex class currently in use returns this error:
Update failed. First exception on row 0 with id 000000000000000; first error: INVALID_ID_FIELD, record id cannot be empty key: []
Error is in expression '{!save}' in component in page masseditcontact: Class.ContactExt.save: line 28, column 1
What I have tried so far is to refer to the field on my visualforce page - Contact.Account.Organization_Size__c - however when I try and update it with the save method in my class it seems to throw the error above.
public class ContactExt {
public Contact record {get; set;}
public String city {
get {
return record.Account.Organization_Size__c;
}
private set;
}
public ContactExt(ApexPages.StandardSetController controller) {
record = (Contact)controller.getRecord();
}
public PageReference save(){
update record
//try{
//update record;
//}
//catch (QueryException e)
//{
//record = new Contact();
//}
return null;
}
}
Visualforce markup
<apex:page standardController="Contact" extensions="ContactExt" recordSetVar="unused" sidebar="true" showHeader="true">
<apex:outputPanel rendered="{!$User.UIThemeDisplayed == 'Theme4d' || contains($CurrentPage.URL, 'lightning.force.com')}">
<apex:stylesheet value="{!URLFOR($Resource.SLDS221, 'assets/styles/salesforce-lightning-design-system-vf.min.css')}" />
<apex:stylesheet value="{!$Resource.MassEditCSS}" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css"></link>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css"></link>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</apex:outputPanel>
<apex:includeScript value="{!$Resource.UtilJS}" />
<apex:includeScript value="{!$Resource.LightningMassEditJS}" />
<apex:includeScript value="support/api/42.0/interaction.js"/>
<apex:includeScript value="support/console/42.0/integration.js"/>
<div class="mass-update-mass-edit" id="mass-update-mass-edit">
<div role="dialog" tabindex="-1" aria-labelledby="header43" class="slds-modal slds-fade-in-open" id="cancel-modal">
<div class="slds-modal__container">
<div class="slds-modal__header">
<button class="slds-button slds-modal__close slds-button--icon-inverse" title="Close" onclick="closeCancelModal();">
<svg class="slds-button__icon slds-button__icon--large" aria-hidden="true">
<use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="{!URLFOR($Resource.SLDS221, '/assets/icons/utility-sprite/svg/symbols.svg#close')}"></use>
</svg>
<span class="slds-assistive-text">Close</span>
</button>
<h2 id="header43" class="slds-text-heading--medium">Return</h2>
</div>
<div class="slds-modal__content slds-p-around--medium">
<p>Are you sure you wish to return?</p>
</div>
<div class="slds-modal__footer">
<button class="slds-button slds-button--neutral" onclick="closeCancelModal();">No</button>
<button class="slds-button slds-button--brand" onclick="goBack();">Yes</button>
</div>
</div>
</div>
<div class="slds-backdrop slds-backdrop--open" id="cancel-modal-backdrop"></div>
<apex:form >
<apex:pageBlock >
<apex:pageMessages />
<apex:pageBlock >
Note: All modifications made on the page will be lost if Return button is clicked without clicking the Save button first.
</apex:pageBlock>
<apex:pageBlockButtons >
<apex:outputPanel rendered="{!$User.UIThemeDisplayed == 'Theme4d' || contains($CurrentPage.URL, 'lightning.force.com')}">
<apex:commandButton value="Save" action="{!save}" status="lightningSavingStatus" reRender="table" styleClass="slds-button slds-button--neutral slds-button--brand" />
<apex:commandButton value="Return" onclick="openCancelModal();" styleClass="slds-button slds-button--neutral" reRender="table" />
<apex:actionStatus id="lightningSavingStatus" >
<apex:facet name="start" >
<div id="spinning" class="slds-spinner_container">
<div class="slds-spinner--brand slds-spinner slds-spinner--medium" role="alert">
<span class="slds-assistive-text">Loading</span>
<div class="slds-spinner__dot-a"></div>
<div class="slds-spinner__dot-b"></div>
</div>
</div>
</apex:facet>
</apex:actionStatus>
</apex:outputPanel>
<apex:outputPanel rendered="{!$User.UIThemeDisplayed != 'Theme4d' && !contains($CurrentPage.URL, 'lightning.force.com')}">
<apex:commandButton value="Save" action="{!save}" status="savingStatus" reRender="table" />
<apex:commandButton value="Return" action="{!cancel}" onclick="return confirmCancel()" />
<apex:actionStatus id="savingStatus" >
<apex:facet name="start" >
<img src="/img/loading.gif" />
</apex:facet>
</apex:actionStatus>
</apex:outputPanel>
</apex:pageBlockButtons>
<apex:pageBlockTable value="{!selected}" var="a" id="table">
<apex:column headerValue="Name">
<apex:inputField value="{!a.Name}"/>
</apex:column>
<apex:column headerValue="Phone">
<support:clickToDial number="{!a.Phone}" entityId="{!a.Id}"/>
</apex:column>
<apex:column headerValue="Mobile Phone">
<apex:inputField value="{!a.MobilePhone}"/>
</apex:column>
<apex:column headerValue="Email">
<apex:inputField value="{!a.Email}"/>
</apex:column>
<apex:column headerValue="Title">
<apex:inputField value="{!a.Title}"/>
</apex:column>
<apex:column headerValue="Account">
<apex:inputField value="{!a.AccountId}"/>
</apex:column>
<apex:column headerValue="Description">
<apex:inputField value="{!a.Description}"/>
</apex:column>
<apex:column headerValue="Organisation Size">
<apex:inputField value="{!a.Organization_Size__c}"/>
</apex:column>
<apex:column headerValue="Organisation Size">
<apex:inputField value="{!a.Account.Organization_Size__c}"/>
</apex:column>
</apex:pageBlockTable>
</apex:pageBlock>
</apex:form>
</div>