Removing a DEFed node that has USEs breaks X3DOM

[mlimper]

as reported on the X3D mailing list:

Let me use the simple DEF/USE example from x3dom.org as example:
http://examples.x3dom.org/example/x3dom_defUse.xhtml

The scene has to nodes, one defining the Shape below Transform#bar, one that is reusing the Shape below Transform#bar.

Now I remove the defining node (using jQuery syntax):
$("Transform#bar Shape").remove();

Now I have an invalid X3D scene in the DOM with a single node pointing to a definition that does not exists. The currently included X3DOM implementation 1.6.2-dev produces an error, stops rendering (displaying both shapes) and gets inactive (I guess this is a bug) . Former versions would just render the "USE" node using the previous definition.