If a device does not have a camera, do not set a camera death notifier

getService("media.camera") will return a NULL binder if there is no
camera service present. This will result in a segfault when we
attempt to set the DeathListener on the binder. If the camera
binder is NULL, we should not attempt to set a notifier.

Bug: 32742216
Bug: 32742421
Change-Id: Id6e7cabdd9e2f0f5d44f4ce435121f84d891026a