[Qemu-block] [PATCH for-4.0] hmp: Fix drive_add ... format=help crash

[Markus Armbruster]

drive_new() returns null without setting an error when it provided
help.  add_init_drive() assumes null means failure, and crashes trying
to report a null error.

Fixes: c4f26c9f37ce511e5fe629c21c180dc6eb7c5a25
Cc: address@hidden
Signed-off-by: Markus Armbruster <address@hidden>
---
 device-hotplug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/device-hotplug.c b/device-hotplug.c
index 6090d5f1e9..6153259d71 100644
--- a/device-hotplug.c
+++ b/device-hotplug.c
@@ -48,7 +48,7 @@ static DriveInfo *add_init_drive(const char *optstr)
 
     mc = MACHINE_GET_CLASS(current_machine);
     dinfo = drive_new(opts, mc->block_default_type, &err);
-    if (!dinfo) {
+    if (err) {
         error_report_err(err);
         qemu_opts_del(opts);
         return NULL;
-- 
2.17.2