fix unable to add/delete new hard disk

Signed-off-by: andy.lee <andy.lee@suse.com>
(cherry picked from commit cbb66175f6)

pkg/harvester/formatters/HarvesterDiskState.vue

@@ -58,7 +58,7 @@ export default {
       const out = [];
 
       blockDevices.map((b) => {
-        if (b.metadata.state.error) {
+        if (b?.metadata?.state?.error) {
           out.push(b.metadata.state.message);
         }
       });