IAE Caused by missing mandatory descendant

BrokerFacade#putDataViaTransaction writes parent (ensureParentsByMerge) before put payload, and causes IllegalArgumentException since its putting an empty containerwhich which has mandatory childs.

java.lang.IllegalArgumentException: Node (http://openconfig.net/yang/bgp?revision=2015-10-09)bgp is missing mandatory descendant /(http://openconfig.net/yang/bgp?revision=2015-10-09)global/config/as

Under BUG-6069 it can be find the step to reproduce the bug.

Just removing ensureParentsByMerge did the fix,
https://git.opendaylight.org/gerrit/#/c/41268/
but it need to be review and finished for someone familiar with the code.
Since not sure what impact it has, and why it has been there in the first place.