how does toLua protect against double delete?

["Eric Ries" <eries@...>]

If you push a C++ object into Lua via toLua, tolua will use tolua_doclone()
to make sure that it gets deleted when Lua loses all references to it. this
is very cool. however, I'm curious what happens if the Lua script author
does and explicit delete() on the object before undoclone() is called - is
there some way to prevent this from happening?