don't crash when we cannot connect to avahi. Fixes #7607

src/common/zeroconf/connection_zeroconf.py

@@ -296,6 +296,7 @@ class ConnectionZeroconf(CommonConnection, ConnectionHandlersZeroconf):
                 show=show))
         else:
             # show notification that avahi or system bus is down
+            self.connected = 0
             gajim.nec.push_incoming_event(OurShowEvent(None, conn=self,
                 show='offline'))
             self.status = 'offline'

src/common/zeroconf/zeroconf_avahi.py

@@ -277,9 +277,10 @@ class Zeroconf:
 
         state = self.server.GetState()
         if state == self.avahi.SERVER_RUNNING:
-            self.create_service()
+            if self.create_service():
             	self.announced = True
             	return True
+            return False
 
     def remove_announce(self):
         if self.announced == False: