Properly fix item duplication bug

Credit to prplz for figuring out the real issue

paper-server/patches/sources/net/minecraft/server/level/ServerPlayer.java.patch

@@ -1477,7 +1477,7 @@
 +
 +    @Override
 +    public boolean isImmobile() {
-+        return super.isImmobile() || !this.getBukkitEntity().isOnline();
++        return super.isImmobile() || (this.connection != null && this.connection.isDisconnected()); // Paper - Fix duplication bugs
 +    }
 +
 +    @Override

paper-server/patches/sources/net/minecraft/server/network/ServerCommonPacketListenerImpl.java.patch

@@ -167,7 +167,7 @@
 +    }
 +
 +    public final boolean isDisconnected() {
-+        return !this.player.joining && !this.connection.isConnected();
++        return (!this.player.joining && !this.connection.isConnected()) || this.processedDisconnect; // Paper - Fix duplication bugs
 +    }
 +    // CraftBukkit end
 +