[Bug]: Encrypt - Having a pending Decrypt request, and triggering`eth_getEncryptionPublicKey`, MetaMask breaks with the error `Cannot read properties of undefined (reading 'charAt')`

### Describe the bug

MetaMask breaks with the error `Cannot read properties of undefined (reading 'charAt')` when clicking Get Encryption Key while having a Decrypt request pending.

Note: in production, MM also breaks, but the error is different, it's: `Cannot read properties of undefined (reading 'balance')`. [This was the ticket for this error](https://github.com/MetaMask/metamask-extension/issues/23344) (which happens in prod 12.5.0)

### Expected behavior

_No response_

### Screenshots/Recordings


https://github.com/user-attachments/assets/94485758-de5a-4a99-819e-c4c4a905e5c0

### Steps to reproduce

1. Go to the test dapp
2. Connect
3. Click Get Encryption Key
4. Accept in MM
5. Add a message and click Encrypt
6. Click Decrypt, without accepting/rejecting in MM
7. Click Get Encryption Key
8. Click Decrypt
9. See MM breaks with error `Cannot read properties of undefined (reading 'charAt')`

### Error messages or log output

_No response_

### Detection stage

During release testing

### Version

12.6.0

### Build type

None

### Browser

Chrome

### Operating system

Linux

### Hardware wallet

_No response_

### Additional context

_No response_

### Severity

_No response_

Start by reproducing the sequence in the test dapp with MetaMask 12.6.0: leave a Decrypt request pending, then trigger eth_getEncryptionPublicKey and another Decrypt request. Trace the UI path handling these concurrent requests and verify that requesting the encryption key no longer breaks MetaMask with an undefined-property error.

Written by the indexing model from the issue text.