Multiple fragments on sub types override each other

[ahanabanerjee]

Describe the bug
If a query has multiple fragments selecting the same sub type, the selected fields override each other

To Reproduce
Steps to reproduce the behavior: Run a query like

query Me {
  loggedInUser {
    id
    ...PicOne
    ...PicTwo
  }
}

fragment PicOne on User {
  profilePicture {
    id
    width
    height
  }
}

fragment PicTwo on User {
  profilePicture {
    id
    url
  }
}

Returns only the fields of the later fragment.

Expected behavior
It should merge the selected sub fields and return both values.