Prop menu won't work

[Tarvik]

As I am using the DarkRP game mode, my props don't seem to appear in my menu. I've already googled for similar errors and had zero progress.
1. fn - gamemodes/sandbox/gamemode/spawnmenu/creationmenu/content/contenttypes/custom.lua:191
2. Call - addons/ulib/lua/ulib/shared/hook.lua:110
3. CallPopulateHook - gamemodes/sandbox/gamemode/spawnmenu/creationmenu/content/content.lua:49
4. Function - gamemodes/sandbox/gamemode/spawnmenu/creationmenu/content/content.lua:80
5. unknown - gamemodes/sandbox/gamemode/spawnmenu/creationmenu.lua:38

[Rubat]

The server you are playing on is out of date. (Or your game is in case of singleplayer)