Hi James,
Open the depot in the view and try to copy/clone the convoy and the game will crash. It only occurs when a line is already selected (like in this case).
savegame: http://server.exp.simutrans.com/debug-saves/classes_crash_when_cloning_vehicle.sve (http://server.exp.simutrans.com/debug-saves/classes_crash_when_cloning_vehicle.sve)
No need to pull from my Github
I think that this is the same as this (http://forum.simutrans.com/index.php?topic=17198.new#new) issue, which I believe that I have now fixed. Would you be able to re-test? I should be grateful.