Even though no addons are installed, the error occurs when opening the server. I can't find any attachments in the Entities tab. it issues a lua error.

[arc9 weapon base] addons/arc9 weapon base/lua/arc9/shared/sh_atts.lua:43: attempt to index a nil value
1. LoadAttachment - addons/arc9 weapon base/lua/arc9/shared/sh_atts.lua:43
2. LoadAtts - addons/arc9 weapon base/lua/arc9/shared/sh_atts.lua:108
3. unknown - addons/arc9 weapon base/lua/arc9/shared/sh_atts.lua:271
4. include - [C]:-1
5. unknown - addons/arc9 weapon base/lua/autorun/sh_arc9_autorun.lua:15