fix(tui): don't process UI events when suspending or stopping (#33710)

When the TUI is suspending or stopping, redraw events should not be
processed, as when it next processes redraw events it's already waiting
for a DA1 response after having disabled some terminal modes.

Fix #33708

src/nvim/ui_client.c

@@ -186,6 +186,7 @@ void ui_client_run(bool remote_ui)
 
 void ui_client_stop(void)
 {
+  ui_client_attached = false;
   if (!tui_is_stopped(tui)) {
     tui_stop(tui);
   }