fix: two crashes, uncovered by the persistent groupchat patch

src/widget/form/groupchatform.cpp

@@ -224,6 +224,11 @@ void GroupChatForm::updateUserNames()
 
     peerLabels.clear();
     const int peersCount = group->getPeersCount();
+
+    // no need to do anything without a peer
+    if (peersCount == 0) {
+        return;
+    }
     peerLabels.reserve(peersCount);
     QVector<QLabel*> nickLabelList(peersCount);
 
@@ -262,6 +267,7 @@ void GroupChatForm::updateUserNames()
     {
         return a->text().toLower() < b->text().toLower();
     });
+
     // remove comma from last sorted label
     QLabel* const lastLabel = nickLabelList.last();
     QString labelText = lastLabel->text();

src/widget/widget.cpp

@@ -1869,8 +1869,8 @@ void Widget::removeGroup(Group* g, bool fake)
         qWarning() << "Tried to remove group" << groupId << "but GroupChatForm doesn't exist";
         return;
     }
-    groupChatForms.erase(groupChatFormIt);
     delete groupChatFormIt.value();
+    groupChatForms.erase(groupChatFormIt);
     delete g;
     if (contentLayout && contentLayout->mainHead->layout()->isEmpty()) {
         onAddClicked();