Migrate to UUID usage

src/main/java/com/lishid/openinv/internal/PlayerDataManager.java

@@ -34,7 +34,7 @@ public class PlayerDataManager {
     public Player loadPlayer(UUID uuid) {
         try {
             OfflinePlayer player = Bukkit.getOfflinePlayer(uuid);
-            if (player == null) {
+            if (player == null || !player.hasPlayedBefore()) {
                 return null;
             }
             GameProfile profile = new GameProfile(uuid, player.getName());

src/main/java/com/lishid/openinv/internal/SpecialPlayerInventory.java

@@ -32,7 +32,7 @@ public class SpecialPlayerInventory extends PlayerInventory {
     private CraftPlayer owner;
     private boolean playerOnline = false;
 
-    public SpecialPlayerInventory(Player p, Boolean online) {
+    public SpecialPlayerInventory(Player p, boolean online) {
         super(((CraftPlayer) p).getHandle());
         this.owner = (CraftPlayer) p;
         this.items = player.inventory.items;