Error while running latest `ami_gui.py`

[Radhu903]

• I tested the latest commit of ami_gui.py on a command-line interface of a Windows 10 machine with 8 GB RAM.
• I am searching corpus activity with the dictionary activity in the abstract section as following:

• It displays the following histograms:

• But When I click on quit, I get the following error:

BUG section should not be List
Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\DELL\AppData\Local\Programs\Python\Python39\lib\tkinter\__init__.py", line 1892, in __call__
    return self.func(*args)
  File "C:\Users\DELL\openDiagram\physchem\python\ami_gui.py", line 509, in run_ami_search
    ami_search.run_search_from_gui(ami_guix)
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 521, in run_search_from_gui
    self.run_search()
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 361, in run_search
    self.analyze_all_words_with_Rake(sections)
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 424, in analyze_all_words_with_Rake
    self.analyze_text_with_Rake(text)
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 436, in analyze_text_with_Rake
    phrases = self.rake.analyze_text_with_RAKE(text)
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 718, in analyze_text_with_RAKE
    self.make_toplevel_phraselist(self.ami_search.ami_gui, phrases)
  File "C:\Users\DELL\openDiagram\physchem\python\search_lib.py", line 724, in make_toplevel_phraselist
    toplevel = tk.Toplevel(master)
  File "C:\Users\DELL\AppData\Local\Programs\Python\Python39\lib\tkinter\__init__.py", line 2621, in __init__
    BaseWidget.__init__(self, master, 'toplevel', cnf, {}, extra)
  File "C:\Users\DELL\AppData\Local\Programs\Python\Python39\lib\tkinter\__init__.py", line 2572, in __init__
    self.tk.call(
_tkinter.TclError: can't invoke "toplevel" command: application has been destroyed