title: Mage registry key "_singleton/awall/feed_extensions" already exists
body: <p>when i laoding admin panel i got this error.</p>
  
  <p>How can i solve this?</p>
  
  <pre><code>There has been an error processing your request
  
  Mage registry key "_singleton/awall/feed_extensions" already exists
  
  Trace:
  #0 /var/www/magento_upgrade/app/Mage.php(222): Mage::throwException('Mage registry k...')
  #1 /var/www/magento_upgrade/app/Mage.php(476): Mage::register('_singleton/awal...', false)
  #2 /var/www/magento_upgrade/app/code/core/Mage/Core/Model/App.php(1316): Mage::getSingleton('awall/feed_exte...')
  #3 /var/www/magento_upgrade/app/Mage.php(447): Mage_Core_Model_App-&gt;dispatchEvent('controller_acti...', Array)
  #4 /var/www/magento_upgrade/app/code/core/Mage/Core/Controller/Varien/Action.php(528): Mage::dispatchEvent('controller_acti...', Array)
  #5 /var/www/magento_upgrade/app/code/core/Mage/Adminhtml/Controller/Action.php(160): Mage_Core_Controller_Varien_Action-&gt;preDispatch()
  #6 /var/www/magento_upgrade/app/code/core/Mage/Core/Controller/Varien/Action.php(408): Mage_Adminhtml_Controller_Action-&gt;preDispatch()
  #7 /var/www/magento_upgrade/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action-&gt;dispatch('index')
  #8 /var/www/magento_upgrade/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
  #9 /var/www/magento_upgrade/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front-&gt;dispatch()
  #10 /var/www/magento_upgrade/app/Mage.php(683): Mage_Core_Model_App-&gt;run(Array)
  #11 /var/www/magento_upgrade/index.php(87): Mage::run('', 'store')
  #12 {main}
  </code></pre>