Date format mixup in the schedule panel

Under Windows, all hell breaks loose when you set a date format like dd/MM/yyyy and you get crashes like:

Application Name: moneyGuru
Version: 1.7.7

Traceback (most recent call last):
  File "C:\src\moneyguru\qt\build\pyi.win32\mg\outPYZ1.pyz/controller.panel", line 89, in lineEditEditingFinished
  File "C:\src\moneyguru\qt\build\pyi.win32\mg\outPYZ1.pyz/core.gui.schedule_panel", line 36, in start_date
  File "C:\src\moneyguru\qt\build\pyi.win32\mg\outPYZ1.pyz/core.app", line 89, in parse_date
  File "C:\src\moneyguru\qt\build\pyi.win32\mg\outPYZ1.pyz/core.model.date", line 318, in parse_date
  File "C:\src\moneyguru\qt\build\pyi.win32\mg\outPYZ1.pyz/_strptime", line 325, in _strptime
ValueError: time data '--/--/----' does not match format '%d-%m-%Y'