Null Callbacks

[Mark Hammons]

Hi,

I'm back with a new wayland problem. More specifically, my problem is 
with a helper library called wlroots. One of its functions, 
wlr_backend_autocreate takes a function pointer as an argument. The big 
problem here is that jextract represents this as a Callback<Fi1>, and 
part of the valid input for this parameter is the null pointer. So the 
question is, how do I create a null callback? Can it even be done with 
foreign as it's currently made?

Thanks,

Mark Hammons