Concatenation of QUrl + string + int is problematic, especially
considering the implicit resolving of strings when assigned to URL
properties like here: an empty faceIconUrl would result in the
qrc:/[...]/Avatar.qml?timestamp=12345 being assigned as the icon URL.

The faceIconUrl property emits two signals in a row during which it
changes to an empty URL and probably back to the same static .icon file
path as before, so all we need to do is to make sure that QtQuick.Image
wouldn't cache it. Thus, the timestamp trick should be irrelevant.