fix for WoW SoD MouseFocus -> MouseFoci

[hexagon5un]

A recent SoD version broke ItemRack by changing a function GetMouseFocus() to GetMouseFoci(), which returns an array instead of a single value.

This patch implements a quick fix that I got on the Simonize rogue discord: https://discord.com/channels/808033004797952021/808070665177399316/1288822112173166676

I'm just pushing it forward. :)