Merge branch '19092-fix-event-for-legacydiffnote-not-considered-note' into 'master'

Fix diff comments not showing up in activity feed

## What does this MR do?

It fixes the detection of note events to check for `Note` and `LegacyDiffNote`.

## Are there points in the code the reviewer needs to double check?

No? /cc @DouweM (since I believe you introduced `LegacyDiffNote`

## Why was this MR needed?

To fix #19092.

## What are the relevant issue numbers?

Fixes #19092.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5069

1 files changed, 2 insertions, 2 deletions

diff --git a/app/models/event.rb b/app/models/event.rb
index d7d23c7ae6d..fd736d12359 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -67,7 +67,7 @@ class Event < ActiveRecord::Base
     elsif issue? || issue_note?
       Ability.abilities.allowed?(user, :read_issue, note? ? note_target : target)
     else
-      ((merge_request? || note?) && target) || milestone?
+      ((merge_request? || note?) && target.present?) || milestone?
     end
   end
 
@@ -136,7 +136,7 @@ class Event < ActiveRecord::Base
   end
 
   def note?
-    target_type == "Note"
+    target.is_a?(Note)
   end
 
   def issue?