[Bug]: Transactions not merged when applying rules to existing transactions

### Verified issue does not already exist?

- [X] I have searched and found no existing issue

### What happened?

1. Create account A
2. Create account B
3. Create a transaction in account A with payee b for an amount of 25.
4. Create a transaction in account B with payee a for an amount of -25.
5. Create rules to replace payee a with the account A, and payee b with the account B.
6. In the edit window for the rules, select the existing transaction and click "Apply actions".

The result is that account A has -50 and account B has 50 due to the transactions not being merged.

### What error did you receive?

_No response_

### Where are you hosting Actual?

None

### What browsers are you seeing the problem on?

_No response_

### Operating System

None