Fix template error when comment review doesn't exist (#29888) (#29889)

Backport #29888

models/fixtures/comment.yml

@@ -75,3 +75,11 @@
   content: "comment in private pository"
   created_unix: 946684811
   updated_unix: 946684811
+
+-
+  id: 9
+  type: 22 # review
+  poster_id: 2
+  issue_id: 2 # in repo_id 1
+  review_id: 20
+  created_unix: 946684810

models/fixtures/review.yml

@@ -170,3 +170,12 @@
   content: "review request for user15"
   updated_unix: 946684835
   created_unix: 946684835
+
+-
+  id: 20
+  type: 22
+  reviewer_id: 1
+  issue_id: 2
+  content: "Review Comment"
+  updated_unix: 946684810
+  created_unix: 946684810