fix panic on storage failed get host (#7390)

pkg/compute/models/hosts.go

@@ -4970,7 +4970,7 @@ func (host *SHost) switchWithBackup(ctx context.Context, userCred mcclient.Token
 	guests2 := host.GetGuestsBackupOnThisHost()
 	for i := 0; i < len(guests2); i++ {
 		if guests2[i].isInReconcile(userCred) {
-			log.Warningf("guest %s is in reconcile", guests[i].GetName())
+			log.Warningf("guest %s is in reconcile", guests2[i].GetName())
 			continue
 		}
 		data := jsonutils.NewDict()

pkg/compute/storagedrivers/rbd.go

@@ -211,6 +211,9 @@ func (self *SRbdStorageDriver) RequestCreateSnapshot(ctx context.Context, snapsh
 func (self *SRbdStorageDriver) RequestDeleteSnapshot(ctx context.Context, snapshot *models.SSnapshot, task taskman.ITask) error {
 	storage := snapshot.GetStorage()
 	host := storage.GetMasterHost()
+	if host == nil {
+		return errors.Errorf("storage %s can't get master host", storage.Id)
+	}
 	url := fmt.Sprintf("%s/disks/%s/delete-snapshot/%s", host.ManagerUri, storage.Id, snapshot.DiskId)
 	header := task.GetTaskRequestHeader()
 	params := jsonutils.NewDict()