NO-JIRA: [Python] Fix exception in IOHandler.on_selectable_expired/update

This occasionally happens after my laptop wakes up from overnight sleep.

IOHandler.on_selectable_expired() is invoked with `selectable` that has
`_terminated=True` and `_transport=None` so when `IOHandler.update()`
is called it crashes when trying to handle the exception
(since transport is None).

Fix this by checking if transport attribute is set and that selectable is not
terminated before invoking `IOHandler.update()`.

Signed-off-by: Ievgen Popovych <[email protected]>

Author: Jmennius

python/proton/_handlers.py

@@ -1234,7 +1234,8 @@ def on_selectable_expired(self, event: Event) -> None:
         t = s._transport
         r = s._reactor
 
-        self.update(t, s, r.now)
+        if not s.is_terminal and t:
+            self.update(t, s, r.now)
 
     def on_connection_local_open(self, event: Event) -> None:
         c = event.connection