qqmlengine: Fix crash when encountering bad singletons

Previously errors occurring when parsing QML singletons would just be ignored resulting in a crash.
The errors are now properly printed and the execution is aborted in time.

Fixes: QTBUG-85932
Change-Id: I61cef5f97546ce2e0753bc46c548838a21b1f506
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index ef9fec56fb..5a20b93c2c 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -2391,6 +2391,12 @@ QJSValue QQmlEnginePrivate::singletonInstance<QJSValue>(const QQmlType &type)
         singletonInstances.convertAndInsert(v4engine(), type, &value);
     } else if (!siinfo->url.isEmpty()) {
         QQmlComponent component(q, siinfo->url, QQmlComponent::PreferSynchronous);
+        if (component.isError()) {
+            warning(component.errors());
+            v4engine()->throwError(QLatin1String("Due to the preceding error(s), Singleton \"%1\" could not be loaded.").arg(QString::fromUtf8(type.typeName())));
+
+            return QJSValue(QJSValue::UndefinedValue);
+        }
         QObject *o = component.beginCreate(q->rootContext());
         value = q->newQObject(o);
         singletonInstances.convertAndInsert(v4engine(), type, &value);