Fix condition stop (#2363)

This pull request fixes a condition in the `stop` method. Previously,
the method would raise a `ValueError` if `output_name` was not provided,
even if it was set to `None`. This pull request updates the condition to
only raise the `ValueError` if `output_name` is not provided and is not
set to `None`. This allows for more flexibility when calling the `stop`
method.

src/backend/base/langflow/custom/custom_component/custom_component.py

@@ -96,7 +96,7 @@ def update_state(self, name: str, value: Any):
     def stop(self, output_name: str | None = None):
         if not output_name and self.vertex and len(self.vertex.outputs) == 1:
             output_name = self.vertex.outputs[0]["name"]
-        else:
+        elif not output_name:
             raise ValueError("You must specify an output name to call stop")
         if not self.vertex:
             raise ValueError("Vertex is not set")