Linux Crossmgr - crash when creating race from xlsx if cmn already exists.

[stuartlynne]

Describe the bug
A clear and concise description of what the bug is.

Trying to create a new race from an existing crossmgr xlsx file, when there is an existing cmn file for the race. A dialogue asks to confirm Overwrite, clicking on OK, Crossmgr exits, and a zero-length cmn file has replaced the previous valid cmn file.

To Reproduce

1. Open a CrossMgr xlsx file with crossmgr to create the cmn file and exit.
2. Repeat

Expected behaviour
Crossmgr should remove the old cmn file and create a new one.

Crossmgr.log

  2025-07-22T18:40:16 (v3.1.79 Linux) New CrossMgr file: "2025-07-09-Gastown-Men Pro 1_2-r3-.cmn"
  Traceback (most recent call last):
    File "/home/sl/CrossMgr-master/CrossMgr.pyw", line 2, in <module>
      MainLoop()
      ~~~~~~~~^^
    File "/home/sl/CrossMgr-master/MainWin.py", line 4386, in MainLoop
      mainWin.openRaceDBExcel( fileName )
      ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
    File "/home/sl/CrossMgr-master/Utils.py", line 627, in new_f
      return f( *args, **kwargs)
    File "/home/sl/CrossMgr-master/MainWin.py", line 3012, in openRaceDBExcel
      properties.commit()                 # Apply the new properties
      ~~~~~~~~~~~~~~~~~^^
    File "/home/sl/CrossMgr-master/Properties.py", line 1528, in commit
      success = SetNewFilename( self, self )
    File "/home/sl/CrossMgr-master/Properties.py", line 1656, in SetNewFilename
      newBaseName = properties.getFileName()
    File "/home/sl/CrossMgr-master/Properties.py", line 1495, in getFileName
      return self.updateFileName()
             ~~~~~~~~~~~~~~~~~~~^^
    File "/home/sl/CrossMgr-master/Properties.py", line 1470, in updateFileName
      gi.date.GetValue().Format(Properties.dateFormat),
      ~~~~~~~~~~~~~~~~^^
  RuntimeError: wrapped C/C++ object of type DatePickerCtrl has been deleted

Desktop (please complete the following information):

• OS: kubuntu 25.04
• Python 3.13.3