JInternalFrame icons are not removed consistently from taskbar when internal frames are closed.
Steps to reproduce:
 - Run SwingSet2 demo.
 - Change the Look and Feel to GTK Style Look And Feel
 - Close the Internal frames in following order: frame0, frame1, frame2, frame3, and frame4
 - Now see some closed frame icon(s) are still present on taskbar of Internal frame demo.
JDK Version: Tiger PIT 10 OCT 2003