From 8352638efc2046b496282ab0ee7a5bc69f79ccef Mon Sep 17 00:00:00 2001
From: Falko Schindler <falko@zauberzeug.com>
Date: Tue, 11 Feb 2025 09:24:34 +0100
Subject: [PATCH] avoid `KeyError` in `handle_disconnect` (fixes #4304)

---
 nicegui/client.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/nicegui/client.py b/nicegui/client.py
index 6ca1119ba..c18deb942 100644
--- a/nicegui/client.py
+++ b/nicegui/client.py
@@ -257,6 +257,8 @@ def handle_disconnect(self, socket_id: str) -> None:
         In contrast to connect handlers, disconnect handlers are not called during a reconnect.
         This behavior should be fixed in version 3.0.
         """
+        if socket_id not in self._socket_to_document_id:
+            return
         document_id = self._socket_to_document_id.pop(socket_id)
         self._cancel_delete_task(document_id)
         self._num_connections[document_id] -= 1