Reset group member list when we are added to the group

This makes test_synchronize_member_list_on_group_rejoin pass.

python/tests/test_account.py

@@ -1438,8 +1438,6 @@ class TestGroupStressTests:
         lp.sec("ac2: check that ac3 is removed")
         msg = ac2.wait_next_incoming_message()
 
-        # ac2 did not see that ac3 was removed
-        # FIXME: due to a bug, ac2 thinks ac3 is still in the chat
         assert len(msg.chat.get_contacts()) == len(chat.get_contacts())
 
 

src/dc_receive_imf.rs

@@ -1023,6 +1023,17 @@ fn create_or_lookup_group(
     // add members to group/check members
     if recreate_member_list {
         if !chat::is_contact_in_chat(context, chat_id, DC_CONTACT_ID_SELF) {
+            // Members could have been removed while we were
+            // absent. We can't use existing member list and need to
+            // start from scratch.
+            sql::execute(
+                context,
+                &context.sql,
+                "DELETE FROM chats_contacts WHERE chat_id=?;",
+                params![chat_id],
+            )
+            .ok();
+
             chat::add_to_chat_contacts_table(context, chat_id, DC_CONTACT_ID_SELF);
         }
         if from_id > DC_CONTACT_ID_LAST_SPECIAL