Gmod Addons Problem

Im trying to install the growing weed plant on my server but when i buy the planter it is invisible and i get and error
The Addon:http://www.garrysmod.org/downloads/?a=view&id=99724

[ERROR] gamemodes/darkrp/entities/entities/weed_plant/cl_init.lua:7: attempt to call method ‘DrawEntityOutline’ (a nil value)

  1. unknown - gamemodes/darkrp/entities/entities/weed_plant/cl_init.lua:7

Help?