Ignore notifications with zero-timing vibrations.

It's now an error to create one of these, but we don't want to crash
system_server because an app passed us a bad value. Instead just catch
the exception and ignore the pattern.

Bug: 36552808
Test: App that posts a notification with all 0 timings. Crashes before
      this patch but not after.

Change-Id: I1f8e2d6d3e7df1186c7a1ce3925e5358cb32290d