Fix error due to unchecked JSON parsing

src/data.lua

@@ -80,7 +80,8 @@ function awards.load()
 		os.rename(old_save_path, minetest.get_worldpath().."/awards.bk.txt")
 		awards.save()
 	else
-		__player_data = minetest.parse_json(storage:get_string("player_data")) or {}
+		local json = storage:get("player_data")
+		__player_data = json and minetest.parse_json(json) or {}
 	end
 end