auto_profiles.lua: don't log warnings on exit

If a script registers hooks before exiting mpv logs "Sending hook
command failed. Removing hook.". (Also there is no function to
unregister hooks.) Don't register hooks in auto_profiles.lua before it
exits to not log these warnings. Fixes 5dc4047. Fixes #15244.

player/lua/auto_profiles.lua

@@ -19,6 +19,8 @@ for _, property in pairs(mp.get_property_native("property-list")) do
     property_set[property] = true
 end
 
+local first_run = true
+
 local function evaluate(profile)
     msg.verbose("Re-evaluating auto profile " .. profile.name)
 
@@ -198,10 +200,14 @@ mp.observe_property("profile-list", "native", function (_, profiles_property)
         return
     end
 
+    if first_run then
+        mp.register_idle(on_idle)
+        for _, name in ipairs({"on_load", "on_preloaded", "on_before_start_file"}) do
+            mp.add_hook(name, 50, on_hook)
+        end
+
+        first_run = false
+    end
+
     on_idle() -- re-evaluate all profiles immediately
 end)
-
-mp.register_idle(on_idle)
-for _, name in ipairs({"on_load", "on_preloaded", "on_before_start_file"}) do
-    mp.add_hook(name, 50, on_hook)
-end