Dont notify about PMs from MUCs we are not joined

The server sends us carbons if one of our other resources has
a conversation in a muc we are not joined.
Instead we log the messages silently.

gajim/common/connection_handlers_events.py

@@ -176,8 +176,10 @@ class HelperEvent:
     def _is_muc_pm(self, message):
         if self.muc_pm is not None:
             return self.muc_pm
-        self.muc_pm = message.getTag(
-            'x', namespace=nbxmpp.NS_MUC_USER) is not None
+        self.muc_pm = False
+        muc_user = message.getTag('x', namespace=nbxmpp.NS_MUC_USER)
+        if muc_user is not None:
+            self.muc_pm = muc_user.getChildren() == []
         return self.muc_pm
 
 class HttpAuthReceivedEvent(nec.NetworkIncomingEvent):
@@ -1599,6 +1601,7 @@ class DecryptedMessageReceivedEvent(nec.NetworkIncomingEvent, HelperEvent):
         self.forwarded = self.msg_obj.forwarded
         self.sent = self.msg_obj.sent
         self.conn = self.msg_obj.conn
+        self.muc_pm = self.msg_obj.muc_pm
         self.popup = False
         self.msg_log_id = None # id in log database
         self.attention = False # XEP-0224

gajim/session.py

@@ -101,7 +101,7 @@ class ChatControlSession(stanza_session.EncryptedStanzaSession):
         if treat_as:
             obj.mtype = treat_as
         pm = False
-        if obj.gc_control and obj.resource:
+        if obj.muc_pm or (obj.gc_control and obj.resource):
             # It's a Private message
             pm = True
             obj.mtype = 'pm'
@@ -123,6 +123,11 @@ class ChatControlSession(stanza_session.EncryptedStanzaSession):
                 additional_data=obj.additional_data,
                 stanza_id=obj.unique_id)
 
+        if obj.muc_pm and not obj.gc_control:
+            # This is a carbon of a PM from a MUC we are not currently
+            # joined. We log it silently without notification.
+            return True
+
         # Handle chat states
         if contact and (not obj.forwarded or not obj.sent):
             if self.control and self.control.type_id == \