title: Python tkinter.ttk combobox throws exception on quit
body: <p>In my Python 3.3 code I use some comboboxes from the ttk library, and they function fine, but if I use any of them, I got an exception when I close the window with the X button. This is an example:</p>
  
  <pre><code>from tkinter import Tk,Label,Button
  from tkinter import ttk
  from tkinter.ttk import Combobox
  
  def cbox_do(event):
      'Used for cbox.'
      clabel.config(text=cbox.get())
  
  a = Tk()
  cbox = Combobox(a, value=('Luke','Biggs','Wedge'), takefocus=0)
  cbox.bind("&lt;&lt;ComboboxSelected&gt;&gt;", cbox_do)
  cbox.pack()
  clabel = Label(a)
  clabel.pack()
  a.mainloop()
  </code></pre>
  
  <p>If you close it without selecting a value, everithing is fine, but try to close it after a value was selected, it exits but prints the following error into the python command line:</p>
  
  <pre><code>can't invoke "winfo" command:  application has been destroyed
      while executing
  "winfo exists $w"
      (procedure "ttk::entry::AutoScroll" line 3)
      invoked from within
  "ttk::entry::AutoScroll .41024560"
      (in namespace inscope "::" script line 1)
      invoked from within
  "::namespace inscope :: {ttk::entry::AutoScroll .41024560}"
      ("uplevel" body line 1)
      invoked from within
  "uplevel #0 $Repeat(script)"
      (procedure "ttk::Repeat" line 3)
      invoked from within
  "ttk::Repeat"
      ("after" script)
  </code></pre>
  
  <p>How could I fix it? I would be grateful for any help you could provide.</p>
  
  <p>Update 1:
  My Python version is v3.3, I use the bundled Tcl/Tk and Tkinter. I tried both the x86 and x64 versions.</p>
  
  <p>Update 2:
  The exception is thrown only if I run my script from command line. It wont show up in Idle.</p>