Poll votes unexpectedly lost when changing vote

[Kirby]

Affected version

2.2.8 PL 1

Steps to Reproduce

1. Create a new poll with two responses and allow to change votes
2. Vote an response 1 with your account
3. Create a new account and vote with that account on response 1 as well
4. Delete the account created in step 3
5. Change your vote to response 2

Expected Result
Response 1 shows 2 votes after step 3, one vote after step 5
OR
Response 1 shows 1 vote after step 3 and zero votes after step 5

Actual Result
Response 1 shows 2 votes after step 3, zero votes after step 5