"About" and "Notes" Windows Only Load on First Opening Attempt

[DavidBerdik]

The "About" and "Notes" windows only load on the first opening attempt. Closing and attempting to reopen them at a later time does not work, and instead an error message prints to the terminal.

To reproduce:

1. Open the "About" window from the PyGAAP GUI.
2. Close it.
3. Attempt to reopen it again.
4. An error message will print to the terminal and no visible change will occur to the GUI.

This is the error that prints in the terminal when replicating this behavior with the "About" window. A similar error prints when doing it using the "Notes" window.

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Program Files\Python 3.10\lib\tkinter\__init__.py", line 1921, in __call__
    return self.func(*args)
  File "C:\PyGAAP\backend\GUI.py", line 711, in displayAbout
    About_page.lift()
  File "C:\Program Files\Python 3.10\lib\tkinter\__init__.py", line 1055, in tkraise
    self.tk.call('raise', self._w, aboveThis)
_tkinter.TclError: bad window path name ".!toplevel"

@Michaeljfang