Incorrect formatting on String built by ValidatorException

See this example test:

@Test
public void facesMessageEmptyDetail()
{
    FacesMessage message = new FacesMessage("Summary", "");
    ValidatorException exception = new ValidatorException(message);

    assertEquals("Summary", exception.getMessage());
} 

It currenty fails as the Exception message being built is "Summary: " because ValidatorException#facesMessageToString only only checks for null, empty strings are not being taken care of.
Actually, if you create a FacesMessage with detail=null it will return the summary as the detail