base: Update latest Dockerfile

- jupyterhub/jupyter-server-proxy#445

base/Dockerfile

@@ -404,6 +404,9 @@ RUN export PIP_BREAK_SYSTEM_PACKAGES=1 \
     nbclassic \
     nbconvert \
     python-lsp-server[all] \
+  ## Fix https://github.com/jupyterhub/jupyter-server-proxy/issues/445
+  && sed -i 's/subprotocols=self\.subprotocols/subprotocols=self\.subprotocols if self\.subprotocols else None/g' \
+    /usr/local/lib/python*/*-packages/jupyter_server_proxy/handlers.py \
   ## Include custom fonts
   && sed -i 's|</head>|<link rel="preload" href="{{page_config.fullStaticUrl}}/assets/fonts/MesloLGS-NF-Regular.woff2" as="font" type="font/woff2" crossorigin="anonymous"></head>|g' /usr/local/share/jupyter/lab/static/index.html \
   && sed -i 's|</head>|<link rel="preload" href="{{page_config.fullStaticUrl}}/assets/fonts/MesloLGS-NF-Italic.woff2" as="font" type="font/woff2" crossorigin="anonymous"></head>|g' /usr/local/share/jupyter/lab/static/index.html \