Not able to display the Related Child record on Visualforce Page

APEX code:

public with sharing class InnerSOQLQuery {


public List<Invoice__c> invList {get;set;}

public List<Item_Detail__c> itemDetail {get;set;}

public void getRelatedRecords(){

itemDetail = new List<Item_Detail__c>();

invList = [SELECT Invoice_Number_c, Product_Detailsc, (SELECT Name, Quantityc, Ratec FROM Item_Detailsr LIMIT 7) FROM Invoice_c WHERE Id = 'a015w00001FG4gz'];

for(Invoice__c Invs:invList){

for( Item_Detail_c itm:Invs.Item_Details_r){
itemDetail.add(itm);
system.debug('Item Name-->'+ itm.Name+ '-->Rate-->'+itm.Rate_c + '-->Quantity-->'+itm.Quantity_c);
}
}
system.debug('Item Name-->'+ itemDetail);

}
}

VF Code>

<apex:page controller="InnerSOQLQuery" docType="html-5.0" standardStylesheets="false" applyBodyTag="false" applyHtmlTag="true">

<apex:pageBlock title="My Content">
<apex:repeat value="{!invList}" var="acct">
<apex:outputText value="{!acct.Product_Details__c}"/>

<apex:repeat value="{!acct.Item_Details__r}" var="obj2">
<apex:outputText value="{!obj2.Name}"/>
</apex:repeat>
</apex:repeat>
</apex:pageBlock>
</apex:page>

Result:

Blank Page

But my Controller shows proper Output while executing via Anonymous window:

It fetches Child records