Since 7f5d9b206d1e ("object-add: don't create return value if
failed"), qmp_object_add() don't write any value in 'ret_data', thus
has random data. Then qobject_unref() fails and abort().
Fix by initialising 'ret_data' properly.
Fixes: 5f07c4d60d09 ("qapi: Flatten object-add")
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200406164207.1446817-1-anthony.perard@citrix.com>
0cd40042c5