--- qtbase/src/widgets/widgets/qtabbar.cpp.orig	2021-12-18 10:09:02.000000000 -0500
+++ qtbase/src/widgets/widgets/qtabbar.cpp	2021-12-18 10:09:53.000000000 -0500
@@ -750,6 +750,8 @@
 {
     Q_Q(QTabBar);
     Q_ASSERT(index >= 0);
+    // play it safe
+    if (index < 0) return;
 
     const Tab *tab = tabList.at(index);
     bool vertical = verticalTabs(shape);
