Added check for zombie ScriptNodes in gui app shutdown.
Added check for zombie ScriptNodes in gui app shutdown.

If I have to go down that rabbit hole again, it'd be nice to have a torch this time.

johnhaddon/gaffer,ImageEngine/gaffer,ivanimanishi/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,cedriclaunay/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,cedriclaunay/gaffer,goddardl/gaffer,hradec/gaffer,chippey/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,lucienfostier/gaffer,boberfly/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,hradec/gaffer,goddardl/gaffer,chippey/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,hradec/gaffer,lucienfostier/gaffer,ImageEngine/gaffer,hradec/gaffer,andrewkaufman/gaffer,boberfly/gaffer,cedriclaunay/gaffer,hradec/gaffer,cedriclaunay/gaffer,goddardl/gaffer,ivanimanishi/gaffer,andrewkaufman/gaffer,boberfly/gaffer,boberfly/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,chippey/gaffer,andrewkaufman/gaffer,chippey/gaffer,appleseedhq/gaffer,GafferHQ/gaffer,goddardl/gaffer