This was comparing the included image-missing icon
with the one in the current icontheme on the test
system. Works fine as long as we don't change
the icons (which we just did). To avoid this, set
the icontheme to hicolor for this test, which does
not have the image-missing icon, so we end up getting
the builtin icon for both ui files.
The position child property is problematic, since it
requires us to emit notification for all children when
inserting a child early in the list of children.
Remove the property from all ui files.
