Always have self.contact of a chat control point to the hightest

resource if none was specified.

As it's still possible to start E2E when the only E2E-capable resource
goes offline, this means that caps is definitely broken.

(Yes, I verified it with a print contact.resource - it IS checked for
the right contact!)

src/chat_control.py

@@ -139,6 +139,13 @@ class ChatControlBase(MessageControl):
 
 	def __init__(self, type_id, parent_win, widget_name, contact, acct,
 	resource = None):
+		if resource is None:
+			# We very likely got a contact with a random resource.
+			# This is bad, we need the highest for caps etc.
+			contact = gajim.contacts. \
+				get_contact_with_highest_priority(
+				acct, contact.jid)
+
 		MessageControl.__init__(self, type_id, parent_win, widget_name,
 			contact, acct, resource = resource);
 

src/gajim.py

@@ -833,6 +833,7 @@ class Interface:
 			ctrl = self.msg_win_mgr.get_control(jid, account)
 			if ctrl:
 				ctrl.set_session(None)
+				ctrl.contact = highest
 
 	def handle_event_msgerror(self, account, array):
 		#'MSGERROR' (account, (jid, error_code, error_msg, msg, time[, session]))