EXECUTE: Open an xhtml file in JBoss Tools HTML editor.
EXECUTE: Open Outline view and expand content of the file in it.
EXECUTE: Open JBoss Tools Palette view, select some element in it, drag it and drop into Outline.
FAILURE: NullPointerException (see npe.txt)

Method DndUtil.getCurrentDragSession() returns null. It seems that simple check for null in getSupportedDataFlavors() solves the problem, and after that drop works properly.