Possible dereference of NULL in block/qapi.c
Description of problem:
qdict_get can return NULL if the "data" key is not found in the obj dictionary. Then if NULL is passed to the qobject_is_empty_dump function, it will be dereferenced when calling the qobject_type function.

https://github.com/qemu/qemu/blob/92ec7805190313c9e628f8fc4eb4f932c15247bd/block/qapi.c#L891-L892

I think that data check for NULL should be added.

Found by Linux Verification Center (portal.linuxtesting.ru) with SVACE.

Author A. Burke.