hmp: fix crash in 'info block -n -v'

The image field in BlockDeviceInfo should never be null, however
bdrv_block_device_info() is not filling it in.

This makes the 'info block -n -v' command crash QEMU.

The proper solution is probably to move the relevant code from
bdrv_query_info() to bdrv_block_device_info(), but since we're too
close to the release for that this simpler workaround solves the
crash.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Message-id: 1429274688-8115-1-git-send-email-berto@igalia.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hmp.c

@@ -391,7 +391,8 @@ static void print_block_info(Monitor *mon, BlockInfo *info,
                         inserted->iops_size);
     }
 
-    if (verbose) {
+    /* TODO: inserted->image should never be null */
+    if (verbose && inserted->image) {
         monitor_printf(mon, "\nImages:\n");
         image_info = inserted->image;
         while (1) {