Warn of control flow with empty statement following

[jonnyboyC]

Provide a warning to the user when a control flow with a body is likely accidentally closed

Examples:

  // will print here
  if true. {
      print("here").
  }

  // will print not possible
  until 10 > 20. {
      print("not possible").
  }

examples such as these are likely always unintentional. We can provide the lowest level diagnostic level "hint" to indicate this is likely unintended without distracting in the rare case it is.