wxWidgets' exception handling gets in the way of debugging by handling uncaught exceptions, thous hiding their point of origin. Luckily this behavior can be disabled. If you're not debugging FreeFileSync, this option doesn't matter, and you can ignore the error.
What about using one of these (as per Strategies for Exception Handling), for minimal exception handling?
- wxApp::OnExceptionInMainLoop()
- wxApp::OnUnhandledException()