Fixed SceneInspector error when deleting node.
Fixed SceneInspector error when deleting node.

This was introduced by the code to remove popup windows when paths become invalid. It seems that it might be a good idea to use WeakMethods in idle callbacks as a general rule

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