libxl: Resolve Coverity NULL_RETURNS

With all the changes in my previous foray into this code, I forgot to
remove the libxlDomainEventQueue(driver, event); call inside the
dom == NULL condition.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

src/libxl/libxl_migration.c

@@ -527,7 +527,6 @@ libxlDomainMigrationFinish(virConnectPtr dconn,
         libxlDomainCleanup(driver, vm, VIR_DOMAIN_SHUTOFF_FAILED);
         event = virDomainEventLifecycleNewFromObj(vm, VIR_DOMAIN_EVENT_STOPPED,
                                          VIR_DOMAIN_EVENT_STOPPED_FAILED);
-        libxlDomainEventQueue(driver, event);
     }
 
  cleanup: