Add the custom CSS handler is self.custom_css is set

Author: jtpio

notebook/app.py

@@ -340,7 +340,8 @@ def initialize_handlers(self) -> None:
         self.handlers.append(("/edit(.*)", FileHandler))
         self.handlers.append(("/consoles/(.*)", ConsoleHandler))
         self.handlers.append(("/terminals/(.*)", TerminalHandler))
-        self.handlers.append(("/custom/custom.css", CustomCssHandler))
+        if self.custom_css:
+            self.handlers.append(("/custom/custom.css", CustomCssHandler))
         super().initialize_handlers()
 
     def initialize(self, argv: list[str] | None = None) -> None:  # noqa: ARG002