QML ComboBox cannot get default image

[hugh]

I'm trying to run a Qt 5.8 QML application on an ARM system (aarch64 - Buildroot), but it's not running properly. When I run it, I get the following errors:

QQuickColorImageProvider: unknown id: "double-arrow/#353637"
file:///usr/qml/QtQuick/Controls.2/ComboBox.qml:66:16: QML Image: Failed to get image from provider: image://default/double-arrow/#353637

It seems that the "default" image provider, which I assume is in-built to support the basic QML types, cannot find the images associated with the ComboBox. I'm wondering if there is something wrong with my Qt5 installation or can I workaround this via a qt.conf file or suchlike? I don't get these errors with the desktop version of the application that I use for development.