messages: set the "discard" logger when exiting

Normally closing a logger should not incur new log messages, but...
the early logger does exactly that, and this prevents it from looping
infinitely into itself. This situation occurs if no proper logger was
installed until the log switch was destroyed.

Fixes #26363.

This effectively reverts
commit e8700cb.

src/misc/messages.c

@@ -322,15 +322,16 @@ static void vlc_vaLogSwitch(void *d, int type, const vlc_log_t *item,
     vlc_rcu_read_unlock();
 }
 
+static void vlc_LogSwitch(vlc_logger_t *logger, vlc_logger_t *new_logger);
+
 static void vlc_LogSwitchClose(void *d)
 {
     struct vlc_logger *logger = d;
     struct vlc_logger_switch *logswitch =
         container_of(logger, struct vlc_logger_switch, frontend);
-    struct vlc_logger *backend = atomic_load_explicit(&logswitch->backend,
-                                                      memory_order_relaxed);
 
-    backend->ops->destroy(backend);
+    /* Discard any further messages. */
+    vlc_LogSwitch(logger, &discard_log);
     free(logswitch);
 }