XF 1.5 Mysqli statement execute error : Column 'user_id' cannot be null

[cat sharp]

when i tired to install addon it showing a error
Server Error
Mysqli statement execute error : Column 'user_id' cannot be null

1. Zend_Db_Statement_Mysqli->_execute() in Zend/Db/Statement.php at line 297
2. Zend_Db_Statement->execute() in Zend/Db/Adapter/Abstract.php at line 479
3. Zend_Db_Adapter_Abstract->query() in XenForo/Model/Conversation.php at line 860
4. XenForo_Model_Conversation->insertConversationRecipient() in XenForo/DataWriter/ConversationMaster.php at line 387
5. XenForo_DataWriter_ConversationMaster->_postSave() in XenForo/DataWriter.php at line 1423
6. XenForo_DataWriter->save() in XenForo/Deferred/UserMessage.php at line 127
7. XenForo_Deferred_UserMessage->_sendMessage() in XenForo/Deferred/UserMessage.php at line 62
8. XenForo_Deferred_UserMessage->execute() in XenForo/Model/Deferred.php at line 295
9. XenForo_Model_Deferred->runDeferred() in XenForo/Model/Deferred.php at line 429
10. XenForo_Model_Deferred->_runInternal() in XenForo/Model/Deferred.php at line 374
11. XenForo_Model_Deferred->run() in XenForo/ControllerAdmin/Tools.php at line 159
12. XenForo_ControllerAdmin_Tools->actionRunDeferred() in XenForo/FrontController.php at line 369
13. XenForo_FrontController->dispatch() in XenForo/FrontController.php at line 152
14. XenForo_FrontController->run() in /home/citie869/public_html/admin.php at line 13