Found and figured out fixes for a couple of Icon selection bugs in the OutfitterBar.lua file:

Changed line 1226 to:
if iconID and not usedIconIDs[iconID] then

Seems that iconID can be 'nil' from the call the GetProfessionInfo and when you pick drop down for your own spellbook you get a error on line 1228, where it attempts to add it to usedIconIDs table.

Also changed lines 1313 to 1315 to:
for vBagSlotIndex = 1, vNumBagSlots do local itemInfo = C_Container.GetContainerItemInfo(vBagIndex, vBagSlotIndex) local vTexture = itemInfo and itemInfo.iconFileID

This relates to an error when you select to pick icons from your own bags.

• The for loop was using 'vSlotIndex' but the name in the call to GetContainerItemInfo said 'vBagSlotIndex', so chose the latter.
• The global 'C_Container' had a typo and said 'C_Containeer'
• Empty bag slots return 'nil' so added a check to prevent itemInfo.iconFileID failing. vTexture is tested for 'nil' later so it's fine if it becomes nil itself.

Either of these errors can be seen by going to the Change Icon option on any outfit and changing the drop down to filter the list.
Hope this helps.

Figured as this is git I should be able to submit a request with the changes I referenced. Hope didn't step on any toes. Thanks for the great addon.