Update simple_menu.py

pycardium/modules/py/simple_menu.py

@@ -362,7 +362,7 @@ class Menu:
                 elif ev == self.button_select:
                     t0 = time.time_ms()
                     long_press = False
-                    while buttons.read(buttons.button_select) > 0:
+                    while buttons.read(self.button_select) > 0:
                         if time.time_ms() - t0 > long_press_ms:
                             long_press = True
                             break