I doing an app using 2 tables in relationship but i'm getting "undefined method `num\_letter' for nil:NilClass"

My tables

```
 index_letters:
   |id|  |num_letter|  

  letter_logs:
  |id|   |index_letter_id|

```

Here is my controller

```
class PolicyManagement::LetterLogController < ApplicationController
   def index_document
     @letter_logs = LetterLog.find(:all)
   end
end

```

My models:

```
class LetterLog < ActiveRecord::Base
   belongs_to :index_letter

end

class  IndexLetter < ActiveRecord::Base
   has_many :letter_logs
end    

```

This is my view

```
<% @letter_logs.each do |letter_log| %>
   <%= letter_log.id %>
   <%= letter_log.index_letter.num_letter %>
<% end %> 

```

I tried this

```
<% @letter_logs.each do |letter_log| %>
   <%= letter_log.id %>
   <%= letter_log.indexletter.num_letter %>
<% end %> 

```

This is my log

```
ActionView::TemplateError (undefined method `num_letter' for nil:NilClass) on line #23 of app/views/policy_management/letter_log/_table.rhtml:

```

New logs:

```
  LetterLog Columns (2.3ms)   SHOW FIELDS FROM `letter_logs`
  IndexLetter Columns (1.2ms)   SHOW FIELDS FROM `index_letters`
  IndexLetter Load (0.2ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 
  CACHE (0.0ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 
  CACHE (0.0ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 
  CACHE (0.0ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 
  CACHE (0.0ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 
  CACHE (0.0ms)   SELECT * FROM `index_letters` WHERE (`index_letters`.`id` = 0) 

```

Please somebody can help me with this? I will really appreciate all help