Dungeon loot: Avoid empty 'if' branch to satisfy lua check

fixes #2228

mods/dungeon_loot/mapgen.lua

@@ -88,18 +88,20 @@ local function populate_chest(pos, rand, dungeontype)
 				amount = rand:next(loot.count[1], loot.count[2])
 			end
 
-			if itemdef.tool_capabilities then
-				for n = 1, amount do
-					local wear = rand:next(0.20 * 65535, 0.75 * 65535) -- 20% to 75% wear
-					table.insert(items, ItemStack({name = loot.name, wear = wear}))
+			if itemdef then
+				if itemdef.tool_capabilities then
+					for n = 1, amount do
+						local wear = rand:next(0.20 * 65535, 0.75 * 65535) -- 20% to 75% wear
+						table.insert(items, ItemStack({name = loot.name, wear = wear}))
+					end
+				elseif itemdef.stack_max == 1 then
+					-- not stackable, add separately
+					for n = 1, amount do
+						table.insert(items, loot.name)
+					end
+				else
+					table.insert(items, ItemStack({name = loot.name, count = amount}))
 				end
-			elseif itemdef.stack_max == 1 then
-				-- not stackable, add separately
-				for n = 1, amount do
-					table.insert(items, loot.name)
-				end
-			else
-				table.insert(items, ItemStack({name = loot.name, count = amount}))
 			end
 		end
 	end