empathy_accounts_dialog_show: check if priv->cms is not NULL before using it
empathy_accounts_dialog_show: check if priv->cms is not NULL before using it

priv->cms is initalized in accounts_dialog_accounts_setup once the
account manager is ready. So it's not garanteed to be set in
empathy_accounts_dialog_show anymore.

GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets