title: Magento error when reindexing "Category Flat Data "
body: <p>I have a strange problem when try to re-indexing "Category Flat Data", I got this error  - "There was a problem with reindexing process."</p>
  
  <p>Here is the exception.log -</p>
  
  <pre><code>DEBUG (7): Exception message: Notice: Undefined offset: 162  in /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Catalog/Model/Resource/Category/Flat.php on line 833
  Trace: #0 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Catalog/Model/Resource/Category/Flat.php(833): mageCoreErrorHandler(8, 'Undefined offse...', '/home/user**/...', 833, Array)
  #1 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Catalog/Model/Resource/Category/Flat.php(528): Mage_Catalog_Model_Resource_Category_Flat-&gt;_getAttributeValues(Array, '1')
  #2 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Catalog/Model/Resource/Category/Flat.php(1482): Mage_Catalog_Model_Resource_Category_Flat-&gt;rebuild()
  #3 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Catalog/Model/Category/Indexer/Flat.php(260): Mage_Catalog_Model_Resource_Category_Flat-&gt;reindexAll()
  #4 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Index/Model/Process.php(210): Mage_Catalog_Model_Category_Indexer_Flat-&gt;reindexAll()
  #5 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Index/Model/Process.php(258): Mage_Index_Model_Process-&gt;reindexAll()
  #6 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Index/controllers/Adminhtml/ProcessController.php(127): Mage_Index_Model_Process-&gt;reindexEverything()
  #7 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Index_Adminhtml_ProcessController-&gt;reindexProcessAction()
  #8 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action-&gt;dispatch('reindexProcess')
  #9 /home/user**/public_html/WEBSITES/*****/app/code/community/Mage/Core/Controller/Varien/Front.php(223): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
  #10 /home/user**/public_html/WEBSITES/*****/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front-&gt;dispatch()
  #11 /home/user**/public_html/WEBSITES/*****/app/Mage.php(684): Mage_Core_Model_App-&gt;run(Array)
  #12 /home/user**/public_html/WEBSITES/*****/index.php(94): Mage::run('', 'store')
  #13 {main}
  </code></pre>
  
  <p>** I have also noticed that Configuration->Catalog->Frontend->Use Flat Catalog Category is set to "No" and I can't changed it to "Yes" as the option is disabled.</p>
  
  <p>Please help me to solve this strange error.</p>