[Change] Mkay, escorts should properly hang if they have no target to

escort.

scripts/ai/tpl/escort.lua

@@ -20,7 +20,7 @@ function escort()
   target = mem.escort
 
   -- Will just float without a target to escort.
-  if target == nil then
+  if not ai.exists(target) then
     return
   end
 

src/ai.c

@@ -266,9 +266,13 @@ static void ai_setMemory(void) {
   L = cur_pilot->ai->L;
 
   lua_getglobal(L, "pilotmem");
+  /* pilotmem */
   lua_pushnumber(L, cur_pilot->id);
+  /* pilotmem, id */
   lua_gettable(L, -2);
+  /* pilotmem, table */
   lua_setglobal(L, "mem");
+  /* pilotmem */
   lua_pop(L, 1);
 }