Call object_properties_init in create_object handlers for PHP 5.4

Apparently if this isn't called from the custom create_object handler,
it leaves the object in a state where extending it and assigning
properties breaks. If this is documented anywhere, I haven't been able
to find it.

Bug: 57292
Change-Id: Icb2b43b78fae7877665321ba973177ed7bffa417