Bug in PopupMenu

[theUser BL]

Tried it with Java8 and Java9. In both is the same bug.

I have tried out the tutorial programs at
http://docs.oracle.com/javafx/2/get_started/jfxpub-get_started.htm
on Linux 64bit.

And that is the result of the popup-window:
http://s16.postimg.org/gt925lvit/Popup_Menu_Bug.png

So the "Fancy Design with CSS" with the coded GUI have the popup-bug.
Here the code: http://docs.oracle.com/javafx/2/get_started/LoginCSS.zip

But the same program created with FXML ("User Interface Design with FXML") have not that bug.
Here the code: http://docs.oracle.com/javafx/2/get_started/FXMLExample.zip

Thats also something, which me wonder. I thought, that there is no difference between creating something with FXML or creating it direct in code, vecause FXML is based on it. But it seems, that it isn't so.

Greatings
theuserbl