error

[ERROR] gamemodes/darkrp/gamemode/modules/base/sh_createitems.lua:529: attempt to call field 'getAvailableVehicles' (a nil value)
  1. createVehicle - gamemodes/darkrp/gamemode/modules/base/sh_createitems.lua:529
   2. unknown - addons/darkrpmodification-master/lua/darkrp_customthings/vehicles.lua:12
    3. include - [C]:-1
     4. loadCustomDarkRPItems - gamemodes/darkrp/gamemode/libraries/modificationloader.lua:111
      5. fn - gamemodes/darkrp/gamemode/libraries/modificationloader.lua:119
       6. unknown - addons/ulib/lua/ulib/shared/hook.lua:183