selected by ipelet problem.

Here is the following reproducible problem (on my laptop, macOS)
if somebody has an idea...


enter few points,
select them
ask for the Delaunay triangulation (or Voronoi or...)  using CGAL ipelets
----> the triangulation appear and is selected
- If I click on the object with right button, then ipe crashes with 
message below
- If I unselect, select again and click with right button, it works well

Olivier


$ ipe
/usr/local/share/ipe/7.1.2/lua/properties.lua:68: bad argument #2 to '?' 
(string expected, got nil)
stack traceback:
     [C]: ?
     /usr/local/share/ipe/7.1.2/lua/properties.lua:68: in function 
'singlePopup'
     /usr/local/share/ipe/7.1.2/lua/properties.lua:45: in function 
'propertiesPopup'
     /usr/local/share/ipe/7.1.2/lua/tools.lua:947: in function 'r'
     /usr/local/share/ipe/7.1.2/lua/tools.lua:975: in function 
</usr/local/share/ipe/7.1.2/lua/tools.lua:951>
     [C]: in function 'mainloop'
     /usr/local/share/ipe/7.1.2/lua/main.lua:385: in main chunk
     [C]: in function 'require'
     [string "require "main""]:1: in main chunk