Check whether the contact exists when saving the contact

Step to reproduce it on Nexus 4 with 4.4.2:
1.Launch Gallery app-->Random select one picture-->"Set picture as"
  -->"Contact photo"-->Random tap one contact-->"Crop picture"-->
  "Just once"-->crop the picture-->press home key
2.Launch People app-->delete the contact which selected in step1-->
  press home key-->Launch Gallery app again-->"Save"
When I set a picture cropped for a contact, before doing the save
operation, I delete the contact, now go on doing the save operation,
because the contact does not exist, the RawContacts is null, so the
function createRawContactDeltaList occurs a crash.

Change-Id: I0de847942850e74035aa865a945c1c5d746e2a69