[Bug]: mUSD Convert: Switching to the same token in the convert screen displays Insufficient funds and zero balance for that token

**Describe the bug**

In the mUSD convert screen, when the same stable coin is selected from the token dropdown, the balance changes to zero and there's an Insufficient funds message displayed.

The issue is fixed by switching to a different token or change token amount manually.

Unable to reproduce on prod build v13.32.1

**Expected behavior**

No insufficient funds message

**Screenshots/Recordings**

https://github.com/user-attachments/assets/e012ea0e-9e36-4a00-a454-c2b27ea11e16

**Steps to reproduce**

1. Have stable coin balance
2. Click Get 3% mUSD bonus
3. Select token and amount
4. Click token dropdown
5. Select the same token
6. Notice balance is 0 and Insufficient funds message

**Error messages or log output**

```shell

```

**Where was this bug found?**

Internal release testing

**Version**

13.33.0

**Build type**

None

**Browser**

Chrome

**Operating system**

MacOS

Start by reproducing the issue in the mUSD convert screen on version 13.33.0, following the listed steps in Chrome on macOS. Trace the token dropdown selection and balance state when the same token is selected; done means the existing balance remains visible and no Insufficient funds message appears.

Written by the indexing model from the issue text.