QQC2 ItemDelegate icon source crashes with custom image provider

I encountered a crash when using an ItemDelegate with a custom image provider:

    delegate: ItemDelegate {
        width: filePage.width
        icon {
            source: "image://ext/" + ext
            width: 32
            height: 32
        }
        text: name
    }

image://ext points to a QQuickAsyncImageProvider subclass. If I replace ItemDelegate with other items with the icon property (e.g. ToolButton) the crash still happens.

Here's a stack trace taken on macOS:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 org.qt-project.QtQml 0x000000010e3704c1 QQmlEngine::imageProvider(QString const&) const + 17
1 org.qt-project.QtQuick 0x000000010de29ab2 QQuickPixmap::load(QQmlEngine*, QUrl const&, QSize const&, QFlags<QQuickPixmap::Option>, QQuickImageProviderOptions const&) + 1090
2 org.qt-project.QtQuick 0x000000010df79d30 QQuickImageBase::load() + 864
3 org.qt-project.QtQuickControls2 0x00000001180b8bdd QQuickIconImagePrivate::updateIcon() + 493
4 org.qt-project.QtCore 0x000000010e8b44eb QMetaObject::activate(QObject*, int, int, void**) + 2347
5 org.qt-project.QtQuick 0x000000010df79762 QQuickImageBase::setSourceSize(QSize const&) + 66
6 org.qt-project.QtQuickControls2 0x00000001180b98cb QQuickIconLabelPrivate::createImage() + 411
7 org.qt-project.QtQuickControls2 0x00000001180b9bfa QQuickIconLabelPrivate::updateOrSyncImage() + 106
8 org.qt-project.QtQuickControls2 0x00000001180c4978 QQuickIconLabel::qt_metacall(QMetaObject::Call, int, void**) + 72
9 org.qt-project.QtQml 0x000000010e402355 QV4::QQmlValueTypeWrapper::write(QObject*, int) const + 165
10 org.qt-project.QtQml 0x000000010e3fd675 GenericBinding<0>::write(QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) + 901