0 may be a valid function, LUA_REFNIL is what we want.

Also don't forget to unref the function on deletion.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Julien Danjou <julien@danjou.info>

event.c

@@ -409,7 +409,7 @@ event_handle_keypress(void *data __attribute__ ((unused)),
     else
     {
         keybinding_t *k = keybinding_find(&globalconf.keys, ev);
-        if (k && k->fct)
+        if (k && k->fct != LUA_REFNIL)
             luaA_dofunction(globalconf.L, k->fct, 0);
     }
 

keybinding.c

@@ -41,6 +41,7 @@ void keybinding_idx_wipe(keybinding_idx_t *idx)
 
 void keybinding_delete(keybinding_t **kbp)
 {
+    luaL_unref(globalconf.L, LUA_REGISTRYINDEX, (*kbp)->fct);
     p_delete(kbp);
 }