In unaccel path we were unconditionaly calling the SourceValidate callback but in some case it could be NULL. Check if we have a valid callback before calling it. Signed-off-by: Jerome Glisse <jglisse@redhat.com> Acked-by: Michel Dänzer <michel@daenzer.net> Signed-off-by: Keith Packard <keithp@keithp.com>