Since: 1.0
Author: Benjamin Eberlei (kontakt@beberlei.de)
Inheritance: extends Doctrine\DBAL\Schema\AbstractSchemaManager
 protected function _getPortableTableColumnDefinition($tableColumn)
 {
     $columnDefinition = parent::_getPortableTableColumnDefinition($tableColumn);
     if ($columnDefinition->getNotnull() === true && empty($columnDefinition->getDefault())) {
         $columnDefinition->setDefault(null);
     }
     return $columnDefinition;
 }