QDoc: Avoid accidental nullptr dereferencing

Coverity complains that `parent` can be dereferenced in the
QDocIndexFiles::readIndexSection function, and indeed it is possible to
create a situation where that happens. This change ensures that the
nullptr check applies equally to the various 'or' conditions in the if
expression.

Coverity-Id: 480819
Pick-to: 6.8
Change-Id: I8c6a9095bc837c772b9a9d699bb5dbe400eb56de
Reviewed-by: Topi Reiniö <[email protected]>
(cherry picked from commit 54423ae)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit c1f1e5a)
Reviewed-by: Paul Wicking <[email protected]>
Reviewed-by: David Boddie <[email protected]>

Author: paulwicking

src/qdoc/qdoc/src/qdoc/qdocindexfiles.cpp

@@ -249,8 +249,8 @@ void QDocIndexFiles::readIndexSection(QXmlStreamReader &reader, Node *current,
             location = Location(indexUrl + QLatin1Char('/') + name);
         else if (!indexUrl.isNull())
             location = Location(name);
-    } else if (elementName == QLatin1String("qmlclass") || elementName == QLatin1String("qmlvaluetype")
-               || elementName == QLatin1String("qmlbasictype")) {
+    } else if (parent && ((elementName == QLatin1String("qmlclass") || elementName == QLatin1String("qmlvaluetype")
+                           || elementName == QLatin1String("qmlbasictype")))) {
         auto *qmlTypeNode = new QmlTypeNode(parent, name,
                     elementName == QLatin1String("qmlclass") ? Node::QmlType : Node::QmlValueType);
         qmlTypeNode->setTitle(attributes.value(QLatin1String("title")).toString());
@@ -272,7 +272,7 @@ void QDocIndexFiles::readIndexSection(QXmlStreamReader &reader, Node *current,
         else if (!indexUrl.isNull())
             location = Location(name);
         node = qmlTypeNode;
-    } else if (elementName == QLatin1String("qmlproperty")) {
+    } else if (parent && elementName == QLatin1String("qmlproperty")) {
         QString type = attributes.value(QLatin1String("type")).toString();
         bool attached = false;
         if (attributes.value(QLatin1String("attached")) == QLatin1String("true"))