"webflow-done" should not be emitted while handling a cancel operation

[RyuzakiKK]

The signal handle-close is handled with handle_request_ref_tokens_close() -> webflow_cancel() -> queue_webflow_finished_once() -> webflow_finished_cb() -> flatpak_authenticator_request_emit_webflow_done().

This means that once it receives the handle-close signal, a new webflow done request will be made.

However, if a webflow is cancelled with flatpak_transaction_abort_webflow(), the variable priv->active_webflow_id will be set to zero. And when "webflow-done" is emitted, the assertion g_assert (priv->active_webflow_id != 0) in request_tokens_webflow_done() will fail.

If I'm reading the specs correctly, when handling the signal handle-close, it should not emit webflow done.