Implement OfflinePlayer#isConnected

paper-server/src/main/java/org/bukkit/craftbukkit/CraftOfflinePlayer.java

@@ -54,6 +54,13 @@ public class CraftOfflinePlayer implements OfflinePlayer, ConfigurationSerializa
         return this.getPlayer() != null;
     }
 
+    // Paper start
+    @Override
+    public boolean isConnected() {
+        return false;
+    }
+    // Paper end
+
     @Override
     public String getName() {
         Player player = this.getPlayer();

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -261,6 +261,13 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
         return this.server.getPlayer(this.getUniqueId()) != null;
     }
 
+    // Paper start
+    @Override
+    public boolean isConnected() {
+        return !this.getHandle().hasDisconnected();
+    }
+    // Paper end
+
     @Override
     public InetSocketAddress getAddress() {
         if (this.getHandle().connection.protocol() == null) return null;