ANDROID: sdcardfs: Check for NULL in revalidate

If the inode is in the process of being evicted,
the top value may be NULL.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 38502532
Change-Id: I0b9d04aab621e0398d44d1c5dc53293106aa5f89
1 file changed