I have some problems during importing products and I have repeated this error in exception.log file.

```
exception 'Exception' with message 'Error during unserialization' in /home/mywebsite.com/xfhrhhemvy/public_html/lib/Unserialize/Parser.php:60
Stack trace:
#0 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Helper/UnserializeArray.php(44): Unserialize_Parser->unserialize('')
#1 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Dataflow/Model/Profile.php(136): Mage_Core_Helper_UnserializeArray->unserialize('')
#2 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Model/Abstract.php(319): Mage_Dataflow_Model_Profile->_afterSave()
#3 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Adminhtml/controllers/System/Convert/ProfileController.php(184): Mage_Core_Model_Abstract->save()
#4 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_System_Convert_ProfileController->saveAction()
#5 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('save')
#6 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#7 /home/mywebsite.com/xfhrhhemvy/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#8 /home/mywebsite.com/xfhrhhemvy/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#9 /home/mywebsite.com/xfhrhhemvy/public_html/index.php(86): Mage::run('', 'store')
#10 {main}

```

Do you have any idea what this error is about? Or how I can find more about it?