Adminhtml layout update xml breaks reindex page

Question

Adding an adminhtml layout update breaks the re-index page here are my xmls.

The third file is an alternative for the layout update with nothing in, which still breaks the index page.

config.xml

<config>
    <adminhtml>
        <layout>
            <updates>
               <index>
                   <file>module/file.xml</file>
               </index>
            </updates>
       </layout>
    </adminhtml>
</config>

module/file.xml

<layout>
    <default>
        <reference name="notifications">
            <block type="module/adminhtml_notifications" name="module_notifications" template="company/module/notifications.phtml"/>
        </reference>
    </default>
</layout>

Still breaks with this: module/file.xml

<layout>

</layout>

Answer 1

Declaring it like this:

   <layout>
        <updates>
           <index>
               <file>module/file.xml</file>
           </index>
        </updates>
   </layout>

tells magento not to use the default layout file for the index module but use your's instead.
So the original layout file is not loaded anymore.

Try declaring it like this:

   <layout>
        <updates>
           <module_index> <!-- this tag must be unique -->
               <file>module/file.xml</file>
           </module_index>
        </updates>
   </layout>