Fix QMultiHash::count(key) crash

As QMultiHash uses a pointer for the data, nullptr dereference is a
thing, so check for valid d before doing anything in count()

Fixes: QTBUG-91704
Change-Id: Ia20440cd7bdc03cb09c77f796fb9c5b52765eac5
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit f226854d256a382a5cc7ff08b10a0d27fbefb0fe)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/qhash/tst_qhash.cpp b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
index 014617f8d4..079b9c6ab7 100644
--- a/tests/auto/corelib/tools/qhash/tst_qhash.cpp
+++ b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
@@ -80,6 +80,8 @@ private slots:
     void hashOfHash();
 
     void stdHash();
+
+    void countInEmptyHash();
 };
 
 struct IdentityTracker {
@@ -1976,5 +1978,18 @@ void tst_QHash::stdHash()
     QVERIFY(!strings.contains("z"));
 }
 
+void tst_QHash::countInEmptyHash()
+{
+    {
+        QHash<int, int> hash;
+        QCOMPARE(hash.count(42), 0);
+    }
+
+    {
+        QMultiHash<int, int> hash;
+        QCOMPARE(hash.count(42), 0);
+    }
+}
+
 QTEST_APPLESS_MAIN(tst_QHash)
 #include "tst_qhash.moc"