Is it OK if dismissModalViewControllerAnimated: gets called before presentModalViewControllerAnimated:?

Question

I'm doing:

if (navigationController.visibleViewController == passcodeInputNav) {
    [navigationController dismissModalViewControllerAnimated:NO];
}

Is the condition unnecessary? Can I just do:

[navigationController dismissModalViewControllerAnimated:NO];

What happens if there's no modal view controller?