gui: when closing the app with a running session and cancel is select…

…ed, avoid closing the app

daemon/core/gui/menubar.py

@@ -357,8 +357,13 @@ def prompt_save_running_session(self, quit_app: bool = False) -> None:
         result = True
         if self.core.is_runtime():
             result = messagebox.askyesnocancel("Exit", "Stop the running session?")
+        # cancel was clicked, avoid doing anything
+        if result is None:
+            return
+        # exit was selected, delete session
         if result:
             self.core.delete_session()
+        # we want to exist the app
         if quit_app:
             self.app.quit()