The last JavaFX window does not get garbage collected

The problem RT-30231 is still present on JavaFX 2.2.x. This record is intended to address it.

Problem description:
Data related JavaFX window is not GCed after the window is closed, even calling GC explicitly. If a new window is open, then the data from the old window is GCed. It seems the framework holds a reference to the closed window which prevents it from being GCed.