binder: NULL pointer reference

This fix handles a possible NULL pointer reference in
debug message.

CRs-fixed: 642883
Change-Id: Ide78f281ec0cff5cbd8231b85c305d13a892854e
Signed-off-by: Paresh Nakhe <pnakhe@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>