Fix "calling 'GetName' on bad self"

In 4.1+ clients, which all modern and classic WoW clients are long
descedents from (all clients are 10.0+ now), GetMouseFocus() can
return nil when opening character frames (player or others like
inspecting).  This fixes calling GetName in those situations.  Its
probably a little overkill, but it works.

ItemRack/ItemRack.lua

@@ -1308,7 +1308,13 @@ end
 
 function ItemRack.MenuMouseover()
 	local frame = GetMouseFocus()
-	if MouseIsOver(ItemRackMenuFrame) or IsShiftKeyDown() or (frame and frame:GetName() and frame:IsVisible() and ItemRack.MenuMouseoverFrames[frame:GetName()]) then
+	local frameName = nil
+	local frameVisible = nil
+	local IRmouseOverFrame = nil
+	if frame then frameName = frame:GetName() end
+	if frame then frameVisible = frame:IsVisible() end
+	if frameName then IRmouseOverFrame = ItemRack.MenuMouseoverFrames[frameName] end
+	if MouseIsOver(ItemRackMenuFrame) or IsShiftKeyDown() or (frame and frameName and frameVisible and IRmouseOverFrame) then
 		return -- keep menu open if mouse over menu, shift is down or mouse is immediately over a mouseover frame
 	end
 	for i in pairs(ItemRack.MenuMouseoverFrames) do