Handle 'sk' being NULL in UID-based routing.

Bug: 15413527
Change-Id: If33bebb7b52c0ebfa8dac2452607bce0c2b0faa0
Signed-off-by: Sreeram Ramachandran <sreeram@google.com>
Git-commit: 0836a0c191f580ed69254e0b287cdce58481e978
Git-repo: https://android.googlesource.com/kernel/common.git
Signed-off-by: Ian Maund <imaund@codeaurora.org>