core: don't callback `self.conn_deferred` if already called: if the connection has been lost (e.g. forced disconnection by server), `self.conn_deferred` may have already been called, thus this is now checked to avoid an exception.

[[Catégorie:Salut à Toi]]
[[Catégorie:documentation développeur]]

= Overview =
This is an autogenerated doc for SàT bridge's API
= Signals =
##SIGNALS_PART##
= Methods =
##METHODS_PART##
----
##TIMESTAMP##