[Bug]: Activity - Loading spinner is invisible (white) for 2nd transaction

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### Describe the bug

Whenever I have submitted 2 transactions right away,I can see how one of them displays a black loading spinner (visible) but the other one a white loading spinner (not visible, only visible when hover)

### Expected behavior

_No response_

### Screenshots/Recordings

https://github.com/user-attachments/assets/9d14f848-a0c0-4adf-9ef7-67694bc31651

### Steps to reproduce

1. Perform Bitcoin Send. (they usually take time so we can test it)
2. Confirm
3. Perform another Bitcoin Send
4. Confirm
5. Check the 2 transactions in the Activity list, 1 with black spinner, the other with white spinner (hover to see)

### Error messages or log output

```shell

```

### Where was this bug found?

Live version (from official store)

### Version

13.38.0

### Build type

None

### Browser

Chrome

### Operating system

MacOS

### Hardware wallet

_No response_

### Additional context

_No response_

### Severity

_No response_

Reproduce this in Chrome on macOS by submitting and confirming two Bitcoin sends in quick succession, then inspect the Activity list rendering and styling for their loading states. Trace why the second spinner becomes white and verify that both transaction spinners remain visible without hovering.

Written by the indexing model from the issue text.