dont render discussion diff unless note is for diff

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/controllers/projects/notes_controller.rb

@@ -86,6 +86,8 @@ class Projects::NotesController < Projects::ApplicationController
   end
 
   def note_to_discussion_with_diff_html(note)
+    return unless note.for_diff_line?
+
     render_to_string(
       "projects/notes/_discussion",
       layout: false,

app/models/note.rb

@@ -183,6 +183,8 @@ class Note < ActiveRecord::Base
   # If exists - its active discussion
   # If not - its outdated diff
   def active?
+    return true unless self.diff
+
     noteable.diffs.each do |mr_diff|
       next unless mr_diff.new_path == self.diff.new_path