Not parsing nested or statement correctly

Hello,

I encountered an issue with the following code:

```pug
mixin h(level, size = xl, align, margin = true, classes = "")
  class= ((size === "xxl" || size === "xl" || size === "l") && margin) ? "mb-s mb-sS@s" : false
```

I expected to get:
```html
class=mb-s mb-sS@s
```

But I actually get:
```html
class=false
```

Thanks!