fix(groups): Fix invalid group list on group member join

The call to Core::getGroupPeerNames is expected to return a list where
the index in the list is the group member id. In any error case we were
previously breaking this constraint. It turns out that every time
someone joins a group we call this function before they have a valid
name resulting in their id not being added to the list.

This fix ensures that the list coming out of Core::getGroupPeerNames
always has a full list.

Fixes #5838

src/core/core.cpp

@@ -1242,6 +1242,7 @@ QStringList Core::getGroupPeerNames(int groupId) const
         TOX_ERR_CONFERENCE_PEER_QUERY error;
         size_t length = tox_conference_peer_get_name_size(tox.get(), groupId, i, &error);
         if (!parsePeerQueryError(error)) {
+            names.append(QString());
             continue;
         }
 
@@ -1250,9 +1251,13 @@ QStringList Core::getGroupPeerNames(int groupId) const
         bool ok = tox_conference_peer_get_name(tox.get(), groupId, i, namePtr, &error);
         if (ok && parsePeerQueryError(error)) {
             names.append(ToxString(name).getQString());
+        } else {
+            names.append(QString());
         }
     }
 
+    assert(names.size() == nPeers);
+
     return names;
 }