title: can't invoke "button" command: application has been destroyed
body: <p>I am first time using tkinter.Some error always show up when i execute this code. I just wanted a gui for a simple python project. errors are 
  widgetName, self._w) + extra + self._options(cnf))
  _tkinter.TclError: can't invoke "button" command: application has been destroyed</p>
  
  <pre><code>import tkinter
  import os
  
  
  MASTER = tkinter.Tk()
  REVIEW_CONTENT_RAW = []
  REVIEWS_SEL_FILM = []
  
  
  
  
  
  
  
  def getReviewFileName(filmNum):
      basepath = os.path.abspath("..").split("/src")
      filepath = basepath[0] + "/resources/reviews"
      filename = filepath + "/review_film" + str(filmNum) +".txt";
      return filename
  
  
  def loadReviewContents():
      global REVIEW_CONTENT
      for i in range(1,6):
          f = open(getReviewFileName(i), mode='r')
          fileContent = f.read().split("\n")
          REVIEW_CONTENT_RAW.append(fileContent)
  
  def getFilmName(filmIndex):
      content = REVIEW_CONTENT_RAW[filmIndex]
      fTitle = content[0]
      return fTitle 
  
  def getReviewListByMovie(filmIndex):
      reviewList = REVIEW_CONTENT_RAW[filmIndex]
      return reviewList
  
  def setReviewsForSelectedFilm(filmIndex):
      global REVIEWS_SEL_FILM
      REVIEWS_SEL_FILM = getReviewListByMovie(filmIndex) 
  
  
  def getReviewsForSelectedFilm():
      return REVIEWS_SEL_FILM
  
  def populateUI():
      loadReviewContents()
      tkinter.Button(MASTER, text=getFilmName(0), 
                     command=buttonClickActionforFilm1).grid(row=1, column=0, sticky=tkinter.W, pady=4)
      tkinter.Button(MASTER, text=getFilmName(1), 
                     command=buttonClickActionforFilm2).grid(row=2, column=0, sticky=tkinter.W, pady=4)
      tkinter.Button(MASTER, text=getFilmName(2), 
                     command=buttonClickActionforFilm3).grid(row=3, column=0, sticky=tkinter.W, pady=4)
      tkinter.Button(MASTER, text=getFilmName(3), 
                     command=buttonClickActionforFilm4).grid(row=4, column=0, sticky=tkinter.W, pady=4)
      tkinter.Button(MASTER, text=getFilmName(4), 
                     command=buttonClickActionforFilm5).grid(row=5, column=0, sticky=tkinter.W, pady=4)
      tkinter.mainloop()
  
      return getReviewsForSelectedFilm()
  
  
  def buttonClickActionforFilm1():
      global MASTER
      setReviewsForSelectedFilm(0)
      MASTER.destroy()
  
  def buttonClickActionforFilm2():
      setReviewsForSelectedFilm(1)
      MASTER.destroy()
  
  def buttonClickActionforFilm3():
      setReviewsForSelectedFilm(2)
      MASTER.destroy()
  
  def buttonClickActionforFilm4():
      setReviewsForSelectedFilm(3)
      MASTER.destroy()
  
  def buttonClickActionforFilm5():
      setReviewsForSelectedFilm(4)
      MASTER.destroy()
  
  
  
  x = populateUI()
  print(x)
  </code></pre>