Is there a way to define the empty sequence?
Consider the example below.
Based on the value from the header one of the bodies is used. However, one header value expects no body at all, and the current implementation does not allow empty "seq:" sequence:
```
"seq: expected array, found null"
```
Is there a way to achieve this?
Or what is fundamentally preventing from allowing the empty sequence?
```yaml
seq:
  - id: header
    type: u8
  - id: body
    type:
      switch-on: header
      cases:
        ' foo_enum::a' : body_a
        ' foo_enum::b' : body_b
        ' foo_enum::c' : body_c
types:
  body_a:
    seq:
      - id: d
        type: u4
  body_b:
    seq:
      - id: e
        type: u8
  body_c:
    seq:
      #should be the empty body
enums:
  foo_enum:
    1: a
    2: b
    3: c
```