mosys: Don't segfault if EC probe fails

BUG=b:110940222
TEST=built and ran on board

Change-Id: I2450e871fda04cffa8d49d907f4df2d216913f45
Reviewed-on: https://chromium-review.googlesource.com/1120686
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Samantha Miller <samanthamiller@google.com>
Reviewed-by: Jason Clinton <jclinton@chromium.org>
1 file changed