Fix reported TooltipScanning error from reputation (#16)

I'm not sure why an index that's within range of GetNumFactions would
return nil data from GetFactionDataByIndex, so we probably need to
figure out what's up with that. Maybe the value returned by
GetNumFactions is only a valid input in some other GetFactionDataBy
variant?

Ref:
* https://www.wowace.com/projects/ice-hud/issues/366
* https://www.curseforge.com/projects/5394?comment=7333

Categories/Reputation.lua

@@ -28,20 +28,22 @@ if C_Reputation and C_Reputation.GetNumFactions then
 	local function iter()
 		for i = 1, GetNumFactions() do
 			local data = GetFactionDataByIndex(i)
-			if data.isHeader == 1 then
-				if data.isCollapsed == 1 then
-					local NumFactions = GetNumFactions()
-					ExpandFactionHeader(i)
-					currentOpenHeader = i
-					NumFactions = GetNumFactions() - NumFactions
-					for j = i+1, i+NumFactions do
-						yield(GetFactionInfo(j))
+			if data then
+				if data.isHeader == 1 then
+					if data.isCollapsed == 1 then
+						local NumFactions = GetNumFactions()
+						ExpandFactionHeader(i)
+						currentOpenHeader = i
+						NumFactions = GetNumFactions() - NumFactions
+						for j = i+1, i+NumFactions do
+							yield(GetFactionInfo(j))
+						end
+						CollapseFactionHeader(i)
+						currentOpenHeader = nil
 					end
-					CollapseFactionHeader(i)
-					currentOpenHeader = nil
+				else
+					yield(data.name, data.description, data.reaction, data.currentReactionThreshold, data.nextReactionThreshold, data.currentStanding)
 				end
-			else
-				yield(data.name, data.description, data.reaction, data.currentReactionThreshold, data.nextReactionThreshold, data.currentStanding)
 			end
 		end
 	end