[Ltib] what's with the empty "bootable_kernel" file in the ISO?

[Robert P. J. Day]

  being incredibly pedantic (and not sure if this is off-topic or  
not), but i'm perusing the contents of the m54[78]x 20080811 ltib  
final ISO image (is there a shorter convention for referring to these  
things?), and i notice the file images/boot/bootable_kernel, which is  
entirely empty.

  doesn't break anything, of course, just looks redundant.  is there  
some reason it's there?

rday