Popup button breaks if used alongside makeLayout
For example:
```nim
 var wnd = newWindow(newRect(40, 40, 800, 600))
 let pb = PopupButton.new(newRect(120, 90, 120, 20))
 pb.items = @["Popup button", "Item 1", "Item 2"]
 v.addSubview(pb)
```
works fine, but adding a makeLayout will break it completely:
```nim
var wnd = newWindow(newRect(40, 40, 800, 600))
wnd.makeLayout:
  - Label as statusText:
      center == super
      size == super
      text: "status"
 let pb = PopupButton.new(newRect(120, 90, 120, 20))
 pb.items = @["Popup button", "Item 1", "Item 2"]
 v.addSubview(pb)
```
In the last case, the popup button appears as text in the upper left corner of the window and is impossible to interact with.