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

fixes #2228

mods/dungeon_loot/mapgen.lua

@@ -88,6 +88,7 @@ local function populate_chest(pos, rand, dungeontype)
 				amount = rand:next(loot.count[1], loot.count[2])
 			end
 
+			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
@@ -103,6 +104,7 @@ local function populate_chest(pos, rand, dungeontype)
 				end
 			end
 		end
+	end
 
 	-- place items at random places in chest
 	local inv = minetest.get_meta(pos):get_inventory()