Merge branch '212842-raise-exception-for-unhandled-todoables-when-emojis-are-added' into 'master'

Return explicit `nil` for all awardables with no todos

Closes #212842

See merge request gitlab-org/gitlab!28605

app/services/award_emojis/add_service.rb

@@ -37,7 +37,8 @@ module AwardEmojis
           awardable.noteable unless awardable.for_personal_snippet?
         when MergeRequest, Issue
           awardable
-        when Snippet
+        else
+          # No todos for all other awardables
           nil
         end
       end