--- qtbase/src/widgets/widgets/qtabbar.cpp.orig	2019-03-14 18:56:40.000000000 -0400
+++ qtbase/src/widgets/widgets/qtabbar.cpp	2019-03-14 18:58:29.000000000 -0400
@@ -721,6 +721,8 @@
 {
     Q_Q(QTabBar);
     Q_ASSERT(index >= 0);
+    // to be safe
+    if (index < 0) return;
 
     Tab &tab = tabList[index];
     bool vertical = verticalTabs(shape);
