AccountModel: do proper sanity check in slotContactRemoved
AccountModel: do proper sanity check in slotContactRemoved

pointers used without checking for nullptr value.

Change-Id: I63eb9b460b44264857ced9ae0aff9bbd634b241c

savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc