title: Rails can't modify frozen string
body: <p>In my controller I have:</p>
  
  <pre><code>def index
      @title = 'asdsadas'
      @kategoris = Tag.where("name like ?", "%#{params[:q]}%")
      respond_to do |format|
      format.html
      format.json { render :json =&gt; @kategoris.map(&amp;:attributes).map{|d| d.map{|d| d.map{|d| d.force_encoding("UTF-8") } } } }
      end
  end
  </code></pre>
  
  <p>I get this error in view:</p>
  
  <pre><code>RuntimeError in Admin::TagsController#index
  
  can't modify frozen string
  </code></pre>