virtio-blk: Fix potential nullpointer read access in virtio_blk_data_…

…plane_destroy

Fixes: CID 1532828
Fixes: b6948ab ("virtio-blk: add iothread-vq-mapping parameter")
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/block/dataplane/virtio-blk.c

@@ -152,14 +152,15 @@ bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
 void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
 {
     VirtIOBlock *vblk;
-    VirtIOBlkConf *conf = s->conf;
+    VirtIOBlkConf *conf;
 
     if (!s) {
         return;
     }
 
     vblk = VIRTIO_BLK(s->vdev);
     assert(!vblk->dataplane_started);
+    conf = s->conf;
 
     if (conf->iothread_vq_mapping_list) {
         IOThreadVirtQueueMappingList *node;