you will need to haxor it in.

basically, in ai_walk, change:

movetogoal();

to

self.enemy = self.goalentity;
movetogoal();
self.enemy = world;

or alternatively, create a movetogoal wrapper only for walking:

void(float step) walktogoal =
{
self.enemy = self.goalentity;
movetogoal();
self.enemy = world;
}

and just replace movetogoal calls with walktogoal in ai_walk.

the wrapper method is probably cleaner and if you make new walking functions, you don't need to repeat the hack.