am 1575202b: am 7a013f96: Fix vold coredump when enable_ums cmd comes without media inserted.

Merge commit '1575202b80942fbbdf770853e775bdad1e8bf87a'

* commit '1575202b80942fbbdf770853e775bdad1e8bf87a':
  Fix vold coredump when enable_ums cmd comes without media inserted.