From d356876a7375936f04abdf0ed57f75e3f177b102 Mon Sep 17 00:00:00 2001
From: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Date: Fri, 1 Jan 2021 11:27:10 +0100
Subject: [PATCH] QAbstractButton: don't access nullptr in queryButtonList()

When a button has no parent, QAbstractButtonPrivate::queryButtonList()
unconditionally accessed parent which results in a nullptr access. Did
not crash because qt_qFindChildren_helper checks for nullptr and
therefore could only be found with a sanitizer.

Fixes: QTBUG-83865
Change-Id: I591e546e96acba50770935b9c3baaf08b09b833d
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>
(cherry picked from commit f0818f6ed8a616dcc94785637039ac21468ef311)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/widgets/qabstractbutton.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/widgets/widgets/qabstractbutton.cpp b/src/widgets/widgets/qabstractbutton.cpp
index 5ced1397b8b..32fbdccfa4d 100644
--- a/src/widgets/widgets/qabstractbutton.cpp
+++ b/src/widgets/widgets/qabstractbutton.cpp
@@ -190,7 +190,9 @@ QList<QAbstractButton *>QAbstractButtonPrivate::queryButtonList() const
         return group->d_func()->buttonList;
 #endif
 
-    QList<QAbstractButton*>candidates = parent->findChildren<QAbstractButton *>();
+    if (!parent)
+        return {};
+    QList<QAbstractButton *> candidates = parent->findChildren<QAbstractButton *>();
     if (autoExclusive) {
         auto isNoMemberOfMyAutoExclusiveGroup = [](QAbstractButton *candidate) {
             return !candidate->autoExclusive()