EXP-1125 FIX -- New tags always shown in Received Items inbox when Inventory...

EXP-1125 FIX -- New tags always shown in Received Items inbox when Inventory window is detached from side panel
EXP-1578 FIX -- received items folder shows shadows of content when scrolling through lots of folders in same window

* Put in guard to prevent the inventory panel from being created multiple times