In this path dressup a bogus machine position is used to get an initial edge, this results in a path element which does reflect the input path data and can lead to a tool crash. This PR checks whether X and Y actually come from the input path data and prevent new path elements being added until true machine position has been set.
Forum thread: https://forum.freecadweb.org/viewtopic.php?f=15&t=42820