Fixed a nil issue that occasionally occurs during addon startup.

diff --git a/CauldronUtil.lua b/CauldronUtil.lua
index 6330d90..cf965a7 100644
--- a/CauldronUtil.lua
+++ b/CauldronUtil.lua
@@ -302,6 +302,11 @@ function Cauldron:GetAutoBuy()
 end

 function Cauldron:MarkRecipeForRescan(skillDB, name)
+
+	if not skillDB then
+		return;
+	end
+
 	-- store rescan info
 	if not skillDB.rescan then
 		skillDB.rescan = {