Comment 2 for bug 1168006

This is causing apps to segfault when calling Theme.loadTheme with this stack trace:

0 UCStyle::unbindItem(QQuickItem*) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf1b8b65
1 ItemStyleAttached::setStyle(UCStyle*) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf1993a3
2 ItemStyleAttached::qt_metacall(QMetaObject::Call, int, void**) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf19af61
3 QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e38750
4 QQmlPropertyPrivate::write(QObject*, QQmlPropertyData const&, QVariant const&, QQmlContextData*, QFlags<QQmlPropertyPrivate::WriteFlag>) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7aba54a
5 QQmlPropertyPrivate::writeValueProperty(QObject*, QQmlPropertyData const&, QVariant const&, QQmlContextData*, QFlags<QQmlPropertyPrivate::WriteFlag>) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abb385
6 QQmlPropertyPrivate::writeBinding(QObject*, QQmlPropertyData const&, QQmlContextData*, QQmlJavaScriptExpression*, v8::Handle<v8::Value>, bool, QFlags<QQmlPropertyPrivate::WriteFlag>) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abc537
7 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7be7767
8 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7be77e7
9 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b5aa59
10 QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b3bb05
11 QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b3bad3
12 QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7aa3a79
13 QMetaObject::activate(QObject*, int, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e590f1
14 QMetaObject::activate(QObject*, QMetaObject const*, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e59d7b
15 ItemStyleAttached::styleChanged() /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf198835
16 ItemStyleAttachedPrivate::updateTheme() /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf1997ae
17 ItemStyleAttachedPrivate::_q_refreshStyle() /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf199e26
18 ?? /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf19a301
19 QMetaObject::activate(QObject*, int, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e59333
20 QMetaObject::activate(QObject*, QMetaObject const*, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e59d7b
21 ThemeEngine::themeChanged() /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf190f05
22 ThemeEnginePrivate::loadTheme(QUrl const&) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf192574
23 ThemeEngine::loadTheme(QUrl const&) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf1926b8
24 ?? /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf192a7f
25 ThemeEngine::qt_metacall(QMetaObject::Call, int, void**) /usr/lib/i386-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so 0xaf192bec
26 QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e38750
27 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7bd6b79
28 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7bd952e
29 QV8QObjectWrapper::Invoke(v8::Arguments const&) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7bd9e51
30 ?? /usr/lib/i386-linux-gnu/libQt5V8.so.5 0xb644e25d
31 ?? 0x3310a336
32 ?? 0x33126964
33 ?? 0x3310db41
34 ?? 0x3314348c
35 ?? 0x33121cb9
36 ?? 0x33112c8a
37 ?? /usr/lib/i386-linux-gnu/libQt5V8.so.5 0xb64783a5
38 ?? /usr/lib/i386-linux-gnu/libQt5V8.so.5 0xb6479ea8
39 ?? /usr/lib/i386-linux-gnu/libQt5V8.so.5 0xb6479fe9
40 v8::Function::Call(v8::Handle<v8::Object>, int, v8::Handle<v8::Value>*) /usr/lib/i386-linux-gnu/libQt5V8.so.5 0xb642256e
41 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b5acdd
42 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b5b290
43 QQmlBoundSignalExpression::evaluate(void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7af2b76
44 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7af3777
45 QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7b3bb05
46 QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7aa3a79
47 QMetaObject::activate(QObject*, int, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e590f1
48 QMetaObject::activate(QObject*, QMetaObject const*, int, void**) /usr/lib/i386-linux-gnu/libQt5Core.so.5 0xb6e59d7b
49 ?? /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7c0f625
50 QQmlVME::complete(QQmlVME::Interrupt const&) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7aca830
51 QQmlComponentPrivate::complete(QQmlEnginePrivate*, QQmlComponentPrivate::ConstructionState*) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abf460
52 QQmlComponentPrivate::completeCreate() /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abf538
53 QQmlComponent::completeCreate() /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abf5ce
54 QQmlComponent::create(QQmlContext*) /usr/lib/i386-linux-gnu/libQt5Qml.so.5 0xb7abf3cc
55 ?? 0x804b276
56 __libc_start_main libc-start.c 260 0xb6959935
57 ?? 0x804d66d