`2022-05-23 13:42:28: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod '' in callback on_playerReceiveFields(): ...orlds/world/worldmods/skinsdb/unified_inventory_page.lua:10: attempt to concatenate field 'standard_inv_bg' (a nil value)
2022-05-23 13:42:28: ERROR[Main]: stack traceback:
2022-05-23 13:42:28: ERROR[Main]: ...orlds/world/worldmods/skinsdb/unified_inventory_page.lua:10: in function 'get_formspec'
2022-05-23 13:42:28: ERROR[Main]: ....worlds/world/worldmods/unified_inventory/internal.lua:84: in function 'get_formspec'
2022-05-23 13:42:28: ERROR[Main]: ...worlds/world/worldmods/unified_inventory/internal.lua:270: in function 'set_inventory_formspec'
2022-05-23 13:42:28: ERROR[Main]: ...worlds/world/worldmods/unified_inventory/api.lua:296: in function 'action'
2022-05-23 13:42:28: ERROR[Main]: ...worlds/world/worldmods/unified_inventory/callbacks.lua:76: in function <...s/worlds/world/worldmods/unified_inventory/callbacks.lua:59>
2022-05-23 13:42:28: ERROR[Main]: ...e/multicraft/bin/../builtin/game/register.lua:441: in function <...e/diakinesis/multicraft/bin/../builtin/game/register.lua:425>
This was the error: