Fixes #6182.  Changed _FormWidget to treat null/undefined/'' the same during onChange processing. Fixed combobox to stop ESC key from closing a dialog if it also closes the popup.
Fixes #6182.  Changed _FormWidget to treat null/undefined/'' the same during onChange processing.
Fixed combobox to stop ESC key from closing a dialog if it also closes the popup.

git-svn-id: 674a2d6b1e32e53f607eb824547723f32280967e@13055 560b804f-0ae3-0310-86f3-f6aa0a117693

harbalk/delite,Sam-Cummins/delite,harbalk/delite,kitsonk/delite,kitsonk/delite,Sam-Cummins/delite