Fix emails on push for new and deleted branches

What does this MR do?

Fix EmailsOnPushWorker when the push is either a new branch or a deleted branch.

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

Don't think so.

Why was this MR needed? / What are the relevant issue numbers?

Closes #20061 (closed).

Does this MR meet the acceptance criteria?

• CHANGELOG entry added (regression)
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together