Comment 1 for bug 540591

The fundamental cause of this crash is a design error: there is no common superclass for SPPath and LivePathEffectObject, and it's not possible to access the LPEObject from the SP tree.

During undo, the selection modification signal doesn't get called, and neither does the LivePathEffectObject deletion signal. At the moment I have no idea how to fix this short of rewriting a significant portion of the SP tree related to LPEs, but maybe I'll find some way.