If you have no sets upon logging in, hovering over the broker will throw an error. An easy way to reproduce this is to make a level one character.

17x Broker_Equipment\Broker_Equipment-40300.20-Release.lua:58: Usage: GameTooltip:SetEquipmentSet("setName")
<in C code>
Broker_Equipment\Broker_Equipment-40300.20-Release.lua:58: in function "OnTooltipShow"
Bazooka\Bazooka-v2.1.4.lua:1401: in function "showTip"
Bazooka\Bazooka-v2.1.4.lua:1224: in function <Bazooka\Bazooka.lua:1215>

Fixed with 48e97de