player/client: reduce log level for hooks not sent to clients

If a hook event can't be sent to a client because it no longer exists,
stop logging it as a warning, as there is no way for a client to remove
hooks, so it is expected that the hook can't be sent. This is documented
in libmpv/client.h.

If the hook event can't be sent because the event queue is full, stop
removing the hook, and keep logging the warning.

player/command.c

@@ -216,9 +216,13 @@ static int invoke_hook_handler(struct MPContext *mpctx, struct hook_handler *h)
     char *name = mp_tprintf(22, "@%"PRIi64, h->client_id);
     int r = mp_client_send_event(mpctx, name, reply_id, MPV_EVENT_HOOK, m);
     if (r < 0) {
-        MP_WARN(mpctx, "Sending hook command failed. Removing hook.\n");
-        hook_remove(mpctx, h);
-        mp_wakeup_core(mpctx); // repeat next iteration to finish
+        if (mp_client_id_exists(mpctx, h->client_id)) {
+            MP_VERBOSE(mpctx, "Sending hook command failed. Removing hook.\n");
+            hook_remove(mpctx, h);
+        } else {
+            MP_WARN(mpctx, "Sending hook command failed.\n");
+            mp_wakeup_core(mpctx); // repeat next iteration to finish
+        }
     }
     return r;
 }