ensure_account: fail if account_new returns NULL.
ensure_account: fail if account_new returns NULL.

Add assert closer to where the error occurs (tp_account_new returns NULL).
The error will get caught eventually by tp_account_prepare, but it's nice
to fail early.

Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib