Anonymous user Unable to signup as a drupal user via event registration option. Crashes the system while submitting registration.

When I try to complete event registration while being a anonymous user wherein the drupal registration required option is enabled on profile, I get the following error:

../sites/all/modules/civicrm/CRM/Core/Error.php, backtrace, 296
../sites/all/modules/civicrm/CRM/Utils/Type.php, fatal, 282
../sites/all/modules/civicrm/CRM/Core/DAO.php, validate, 933
../sites/all/modules/civicrm/CRM/Core/DAO.php, composeQuery, 870
../sites/all/modules/civicrm/CRM/Contact/BAO/GroupContact.php, executeQuery, 405
../sites/all/modules/civicrm/api/v2/GroupContact.php, getContactGroup, 66
../sites/all/modules/civicrm/drupal/modules/civicrm_group_roles/civicrm_group_roles.module, civicrm_group_contact_get, 86
../modules/user/user.module, civicrm_group_roles_user_login, 101
../modules/user/user.module, user_module_invoke, 2225
../modules/user/user.module, user_login_finalize, 2238
../modules/user/user.module, user_login_submit, 3793
../includes/form.inc, user_register_submit, 1430
../includes/form.inc, form_execute_handlers, 844
../sites/all/modules/civicrm/CRM/Core/BAO/CMSUser.php, drupal_process_form, 535
../sites/all/modules/civicrm/CRM/Core/BAO/CMSUser.php, createDrupalUser, 131
../sites/all/modules/civicrm/CRM/Event/Form/Registration.php, create, 821
../sites/all/modules/civicrm/CRM/Event/Form/Registration/Confirm.php, confirmPostProcess, 634
../sites/all/modules/civicrm/CRM/Core/Form.php, postProcess, 250
../sites/all/modules/civicrm/CRM/Core/StateMachine.php, mainProcess, 167
../sites/all/modules/civicrm/CRM/Core/QuickForm/Action/Next.php, perform, 64
../sites/all/modules/civicrm/packages/HTML/QuickForm/Controller.php, perform, 203
../sites/all/modules/civicrm/packages/HTML/QuickForm/Page.php, handle, 103
../sites/all/modules/civicrm/CRM/Core/Controller.php, handle, 284
../sites/all/modules/civicrm/CRM/Core/Invoke.php, run, 224
../sites/all/modules/civicrm/drupal/civicrm.module, invoke, 447
, civicrm_invoke,
../includes/menu.inc, call_user_func_array, 503
../index.php, menu_execute_active_handler, 21

There is no problem when I login as a drupal user and then try to register for an event.