Fatal error: Call to a member function addToChildGroup() app/code/core/Mage/Core/Block/Abstract.php on line 759

Question

I have added this code for block in catalog.xml and i got following error -

Fatal error: Call to a member function addToChildGroup() app/code/core/Mage/Core/Block/Abstract.php on line 759

<!-- custom change here-->

<block type="catalog/product_list_related" name="catalog.product.related" as="product_additional_data" after="product.info.upsell" template="catalog/product/list/related.phtml"/>

<action method="setColumnCount"><columns>4</columns></action>                    

                <action method="setItemLimit"><type>related</type><limit>4</limit></action>
</block>
<!-- custom change  here-->                            

Answer 1

You closed your block here:

<block ... />

I suppose that causes the error.

Try this code:

<block type="catalog/product_list_related" name="catalog.product.related" as="product_additional_data" after="product.info.upsell" template="catalog/product/list/related.phtml">
  <action method="setColumnCount">
    <columns>4</columns>
  </action>                    
  <action method="setItemLimit">
    <type>related</type>
    <limit>4</limit>
  </action>
</block>

Answer 2

I got similar kind of problem when I worked on github repository.I installed an extension on the local system then pushed the code to GitHub. Next day when I removed extension from github and moved the code to development server.Then I faced same kind of problem.

For me clearing the caches worked