nvme_subsys_ctrl() is used in contexts where the given controller
identifier is from an untrusted source. Like its friends nvme_ns() and
nvme_subsys_ns(), nvme_subsys_ctrl() should just return NULL if an
invalid identifier is given.
Fixes: 645ce1a70cb6 ("hw/block/nvme: support namespace attachment command")
Cc: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
7645f21f40