update contact instance in chat window when we talk to another resource. Fixes #7700

src/common/connection.py

@@ -463,8 +463,9 @@ class CommonConnection:
                 msg_iq = iqs
         else:
             msg_iq.setTo(fjid)
-            if resource:
-                contact = gajim.contacts.get_contact(self.name, jid, resource)
+            r_ = resource or gajim.get_resource_from_jid(fjid)
+            if r_:
+                contact = gajim.contacts.get_contact(self.name, jid, r_)
             else:
                 contact = gajim.contacts.get_contact_with_highest_priority(
                     self.name, jid)

src/session.py

@@ -160,6 +160,7 @@ class ChatControlSession(stanza_session.EncryptedStanzaSession):
             if ctrl:
                 self.control = ctrl
                 self.control.set_session(self)
+                self.control.contact = contact
 
         if not pm:
             self.roster_message2(obj)