NoMethodError in AppsController#download

undefined method `id' for nil:NilClass

Extracted source (around line #246):
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if @articles.length == 0
@articles = Post.joins("INNER JOIN posts_sub_category_apps ON posts.id = posts_sub_category_apps.post_id")
.published.where("posts_sub_category_apps.sub_category_app_id = #{@app.sub_category_app.id}").take(4)
end
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Rails.root: /srv/http/netxee3.dev

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"device"=>"android", "download"=>"descargar"}

Response

Headers:

None