Commit f1b34a248e9 replaced less-than-obvious test in
qdict_flatten_qdict() by the obvious one. Sadly, it made something
else non-obvious: the fact that @new_key passed to qdict_put_obj()
can't be null, because that depends on the function's precondition
(target == qdict) == !prefix.
Tweak the function some more to help Coverity and human readers alike.
Fixes: CID 1393620
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>