"line following route" as two points per point. #3247
Description
When you draw a line with the "line following route" (sorry, I don't know the name in English ("Dessiner en suivant les routes" in French), two points seems to exist for the same coordinates, thus making several kind of bug. I think the bugs are due to the same issue, so I only post it as one bug.
Here is how to reproduce.
Bug example number 1
Draw a line (line following route)
Press "ctrl + Z" to come back to the previous points.
The line is erased but some the points are still present.
Bug example number 2
Draw a line (line following route) and edit the end to continue from the last point.
Once you did add a point, try to do the same thing (edit the end to continue from the last point). You can't.
But if you erase the last point, a "twin point" is still existing and you can again edit the end to continue from the last point
