Previously Web Flow's BindingResult implementation distinguished
object from field-level errors by checking if the source of the
error is null or otherwise a String. However, class-level bean
validation errors have a field source represented by an empty
String. After this change object and field-level errors are
recognized by checking for String-based field source that is
neither null nor empty.
This commit also contains a fix for spring-faces tests where
in JSF 2.1 the presence of an unreleased FacesContext may
cause some tests to fail.
df649084ab