Fix Manual Bed Leveling with multiple extruders (#16688)

Marlin/src/lcd/menu/menu_filament.cpp

@@ -119,7 +119,7 @@ void _menu_temp_filament_op(const PauseMode mode, const int8_t extruder) {
           SUBMENU_N_P(s, msg, []{ _menu_temp_filament_op(PAUSE_MODE_CHANGE_FILAMENT, MenuItemBase::itemIndex); });
         else {
           ACTION_ITEM_N_P(s, msg, []{
-            char cmd[12];
+            char cmd[13];
             sprintf_P(cmd, PSTR("M600 B0 T%i"), int(MenuItemBase::itemIndex));
             lcd_enqueue_one_now(cmd);
           });