Fix crash on hovering over legacy shared items

spec/System/TestItemMods_spec.lua

@@ -33,6 +33,20 @@ describe("TetsItemMods", function()
 		assert.are.equals(2, legacyLines)
 	end)
 
+	it("shows a fallback tooltip when an item's base is no longer supported", function()
+		local item = new("Item", [[
+			Rarity: Unique
+			Legacy Item
+			Removed Base
+		]])
+		local tooltip = new("Tooltip")
+
+		assert.has_no.errors(function()
+			build.itemsTab:AddItemTooltip(tooltip, item)
+		end)
+		assert.is_truthy(tooltip.lines[#tooltip.lines].text:find("Item base is not supported", 1, true))
+	end)
+
 	it("aggregates matching ring item rarity lines before applying ring bonus effect", function()
 		build.configTab.input.customMods = "30% increased bonuses gained from left Equipped Ring"
 		build.configTab:BuildModList()

src/Classes/ItemsTab.lua

@@ -3232,6 +3232,13 @@ function ItemsTabClass:AddItemTooltip(tooltip, item, slot, dbMode, maxWidth)
 	tooltip.tooltipHeader = item.rarity
 	tooltip.center = true
 	tooltip.color = rarityCode
+	-- Shared items can use old base names that no longer exist. Add a tooltip so they can be copied or removed without causing a crash.
+	if not item.base or not item.baseName then
+		tooltip:AddLine(fontSizeTitle, rarityCode..(item.title or item.name or "Unknown Item"), "FONTIN SC")
+		tooltip:AddSeparator(30)
+		tooltip:AddLine(fontSizeTitle, colorCodes.NEGATIVE.."Item base is not supported by the current version.", "FONTIN SC")
+		return
+	end
 	-- Item name
 	if item.title then
 		tooltip:AddLine(fontSizeTitle, rarityCode..item.title, "FONTIN SC")