If your app crashes on iOS please do the following to save your data:
Download the trial version:
This is the previous app version that should still work.
You will get a warning that your data might be lost, but this is not the case.
With this you should hopefully be able to export the birthdays as a file.
If the data is saved you can uninstall the app and install the AppStore version. I apologize for the inconvenience.