Damagelogs Script Errors

[ERROR] addons/tttdamagelogs-master/lua/damagelogs/cl_damagelog.lua:138: bad argument #1 to ‘IsKeyDown’ (number expected, got nil)

  1. IsKeyDown - [C]:-1
  2. Think - addons/tttdamagelogs-master/lua/damagelogs/cl_damagelog.lua:138
    3. fn - addons/tttdamagelogs-master/lua/damagelogs/cl_damagelog.lua:156
    4. unknown - addons/ulib/lua/ulib/shared/hook.lua:110

What does this mean? I got this after adding groups to see the RDM Manager.