Candlestick with empty theme bug

A `<VictoryCandlestick>` component with an empty theme does not render labels correctly.

Reproduction:

```
<VictoryCandlestick labels theme={{}} />
```

Expected:

![Image](https://github.com/user-attachments/assets/2a0b1664-0d6c-4875-b7a9-7d236e6c7bc2)

Actual:

`TypeError: Cannot read properties of undefined (reading 'padding')`

