Waveform shows 'x' when driving signal with 'z'

### Describe the bug

RTL Output correctly shows z's being assigned, but waveform shows X's. Seems like waveform only shows z's when a signal not driven.

```
// combinational
always_comb begin
unique case (currentState)
2'h0 : begin
len = len_f;
dstAddr = dstAddr_f;
srcAddr = srcAddr_f;
mem_req_valid = 1'h0;
mem_req_is_read = 1'h0;
mem_req_data = 32'bzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz;
```

### To Reproduce

Drive signal to 'z inside action argument of the FiniteStateMachine class.

e.g.
` io.mem.req.data < Const(LogicValue.z, width: 32),
`
### Expected behavior

Waveform to show Zs

### Actual behavior

Shows x's


### Additional: Dart SDK info

_No response_

### Additional: pubspec.yaml

```yaml

```

### Additional: Context

_No response_