If you are on a character that has info saved on the Legendary cloak progression, and for whatever reason you unequip said cloak and open SI, it breaks, as in it show nothing but an empty frame with the following message from bugsack:

1x bad argument #1 to '?' (Usage: local currentItemLevel = C_Item.GetCurrentItemLevel(itemLocation))
[string "=[C]"]: in function GetCurrentItemLevel' [string "@SavedInstances\SavedInstances-8.3.3.lua"]:1709: in function UpdateToonData'
[string "@SavedInstances\SavedInstances-8.3.3.lua"]:3601: in function ShowTooltip' [string "@SavedInstances\SavedInstances-8.3.3.lua"]:3482: in function ShowDetached'
[string "@SavedInstances\SavedInstances-8.3.3.lua"]:3432: in function ToggleDetached' [string "@SavedInstances\SavedInstances-8.3.3.lua"]:2710: in function OnClick'
[string "@BugSack\Libs\LibDBIcon-1.0\LibDBIcon-1.0-43.lua"]:144: in function <BugSack\Libs\LibDBIcon-1.0\LibDBIcon-1.0.lua:142>

Locals:
(*temporary) = "bad argument #1 to '?' (Usage: local currentItemLevel = C_Item.GetCurrentItemLevel(itemLocation))"

Re-equipping the cloak fixes it without any further action. Tested it with multiple characters and with no other addons than SavedInstances as well. The issue is the same.