don't create a new session when we get an error message in a pm. Fixes #7435

src/common/connection_handlers.py

@@ -1367,6 +1367,17 @@ class ConnectionHandlersBase:
         else:
             return None
 
+    def get_latest_session(self, jid):
+        """
+        Get the session that we last sent a message to
+        """
+        if jid not in self.sessions:
+            return None
+        sessions = self.sessions[jid].values()
+        if not sessions:
+            return None
+        return sorted(sessions, key=operator.attrgetter('last_send'))[-1]
+
     def find_controlless_session(self, jid, resource=None):
         """
         Find an active session that doesn't have a control attached

src/common/connection_handlers_events.py

@@ -1109,6 +1109,15 @@ class MessageReceivedEvent(nec.NetworkIncomingEvent, HelperEvent):
 
         self.session = None
         if self.mtype != 'groupchat':
+            if gajim.interface.is_pm_contact(self.fjid, account) and \
+            self.mtype == 'error':
+                self.session = self.conn.find_session(self.fjid, self.thread_id)
+                if not self.session:
+                    self.session = self.conn.get_latest_session(self.fjid)
+                if not self.session:
+                    self.session = self.conn.make_new_session(self.fjid,
+                        self.thread_id, type_='pm')
+            else:
                 self.session = self.conn.get_or_create_session(self.fjid,
                     self.thread_id)