In the Items plugin, getItemLevelText() returns nil when options.showEquipmentItemLevels ~= true.

This causes an error when the result is later concatenated with a string, such as here on line 298.

Thanks for reporting this, I'll clean up that code a bit as it's pretty inconsistent across that plugin and will fix that issue in there.
The fix should be out some time tomorrow.

This was fixed in version 3.22.