Non valid behavior for attribute - key: value (object)

[klokane]

For following blueprint

# GET /
- Response 200 (application/json)
    - Attribute (A)

# Data Structures

## A
- myObject: abc (object)

I will receive message

warning: (1)  unable to render JSON/JSONSchema. Invalid member type of object in MSON definition :11:32

Expected behavior is report invalid syntax for definition - myObject: abc (object)

[w-vi]

This I think requires to have semantical check phase in drafter, as this is syntactically correct but because it is an object it doesn't make sense.