Development Assistance Can't build with Simple Scoreboard (Designed for Bukkit)

Hey guys.
I'm using the Bukkit Dev Util "Simple Scoreboards" with a Spigot server, but i can't build the scoreboard. The scoreboard is to display online staff. Could you maybe give me a hint if i could change anything?

Code that affects the scoreboard:

Code:java

    @EventHandler
    public void onLogin(PlayerJoinEvent event) {
        Player player = event.getPlayer();
        SimpleScoreboard scoreboard = new SimpleScoreboard("§a§lStaff inne just nu:");
 
 
        for (int a = 0; a <= online().size(); a++){
            if(online().size() > 0)
            scoreboard.add("&c" + online().get(a));
            else
            scoreboard.add("&c&lIngen staff inne just nu!");
 
        }
        scoreboard.build();
        for(Player p : Bukkit.getOnlinePlayers()) {
            scoreboard.send(p); 
            }
}
 
    public List<String> online() {
        List<String> output = new ArrayList<String>();
        for (Player player : Bukkit.getOnlinePlayers()) {
            if (player.hasPermission("essentials.kick")) {
                output.add(player.getName());
            }
        }
        return output;
 
    }

SimpleScoreboard code:

Code:java

public class SimpleScoreboard {
 
        private Scoreboard scoreboard;
 
        private String title;
        private Map<String, Integer> scores;
        private List<Team> teams;
 
        public SimpleScoreboard(String title) {
                this.scoreboard = Bukkit.getScoreboardManager().getNewScoreboard();
                this.title = title;
                this.scores = Maps.newLinkedHashMap();
                this.teams = Lists.newArrayList();
        }
 
 
 
        public void blankLine() {
                add(" ");
        }
 
        public void add(String text) {
                add(text, null);
        }
 
        public void add(String text, Integer score) {
                Preconditions.checkArgument(text.length() < 48, "text cannot be over 48 characters in length");
                text = fixDuplicates(text);
                scores.put(text, score);
        }
 
        private String fixDuplicates(String text) {
                while (scores.containsKey(text))
                        text += "§r";
                if (text.length() > 48)
                        text = text.substring(0, 47);
                return text;
        }
 
        private Map.Entry<Team, String> createTeam(String text) {
                String result = "";
                if (text.length() <= 16)
                        return new AbstractMap.SimpleEntry<>(null, text);
                Team team = scoreboard.registerNewTeam("text-" + scoreboard.getTeams().size());
                Iterator<String> iterator = Splitter.fixedLength(16).split(text).iterator();
                team.setPrefix(iterator.next());
                result = iterator.next();
                if (text.length() > 32)
                        team.setSuffix(iterator.next());
                teams.add(team);
                return new AbstractMap.SimpleEntry<>(team, result);
        }
 
        public void build() {
                Objective obj = scoreboard.registerNewObjective((title.length() > 16 ? title.substring(0, 15) : title), "dummy");
                obj.setDisplayName(title);
                obj.setDisplaySlot(DisplaySlot.SIDEBAR);
 
                int index = scores.size();
 
                for (Map.Entry<String, Integer> text : scores.entrySet()) {
                        Map.Entry<Team, String> team = createTeam(text.getKey());
                        Integer score = text.getValue() != null ? text.getValue() : index;
                        OfflinePlayer player = Bukkit.getOfflinePlayer(team.getValue());
                        if (team.getKey() != null)
                                team.getKey().addPlayer(player);
                        obj.getScore(player).setScore(score);
                        index -= 1;
                }
        }
 
        public void reset() {
                title = null;
                scores.clear();
                for (Team t : teams)
                        t.unregister();
                teams.clear();
        }
 
        public Scoreboard getScoreboard() {
                return scoreboard;
        }
 
        public void send(Player... players) {
                for (Player p : players)
                        p.setScoreboard(scoreboard);
        }
 
}

Error:

Code:

[19:56:27 ERROR]: Could not pass event PlayerJoinEvent to StaffSB v1
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:305) ~[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:62) ~[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.j
ava:502) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:487) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.PlayerList.onPlayerJoin(PlayerList.java:
262) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.PlayerList.a(PlayerList.java:147) [spigo
t.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.LoginListener.b(LoginListener.java:109)
[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.LoginListener.c(LoginListener.java:41) [
spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.NetworkManager.a(NetworkManager.java:159
) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.ServerConnection.c(ServerConnection.java
:82) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:7
85) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:3
16) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:6
23) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java
:526) [spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_25]
Caused by: java.lang.IllegalArgumentException: Name cannot be blank
        at com.google.common.base.Preconditions.checkArgument(Preconditions.java
:125) ~[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at org.bukkit.craftbukkit.v1_8_R1.CraftServer.getOfflinePlayer(CraftServ
er.java:1275) ~[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        at org.bukkit.Bukkit.getOfflinePlayer(Bukkit.java:741) ~[spigot.jar:git-
Spigot-9a88a38-bab0e8b]
        at se.Fillefixsweden.StaffSB.SimpleScoreboard.build(SimpleScoreboard.jav
a:86) ~[?:?]
        at se.Fillefixsweden.StaffSB.Main.onLogin(Main.java:50) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0
_25]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0
_25]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1
.8.0_25]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_25]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:301) ~[spigot.jar:git-Spigot-9a88a38-bab0e8b]
        ... 14 more

Thank you in advance!