          else:
              retval = None
          return retval
  
      def _remove_dummy_master(self):
          """ Destroy the dummy master widget on Linux systems. """
          if platform.system().lower() != "linux":
              return
          self._dummy_master.destroy()
          del self._dummy_master
 
</s> remove         if platform.system().lower() != "linux":
 </s> add         if platform.system().lower() != "linux" or self._dummy_master is None: </s> remove             retval = tk.Frame()
            retval.option_add("*foreground", "black")
 </s> add             frame = tk.Frame()
            frame.option_add("*foreground", "black")
            retval: Optional[tk.Frame] = frame </s> remove     def _set_defaults(self):
 </s> add     def _set_defaults(self) -> Dict[str, Optional[str]]: </s> remove     def run(self):
 </s> add     def run(self) -> None: </s> remove         retval = dict()
 </s> add         retval = {}
    def _remove_dummy_master(self) -> None:
          else:
              retval = None
          return retval
  
    def _remove_dummy_master(self) -> None:
          """ Destroy the dummy master widget on Linux systems. """
          if platform.system().lower() != "linux":
              return
          self._dummy_master.destroy()
          del self._dummy_master
keep keep keep keep replace keep keep keep keep keep
 Bugfix: Preview for extract in batch mode 
lib/gui/utils.py