cli: Fix a panic in deployment status when scheduling is slow

If a deployment fails, the `deployment status` command can get a nil deployment
when it checks for a rollback deployment if there isn't one (or at least not one
at the time of the query). Fix the panic.

command/deployment_status.go

@@ -332,7 +332,7 @@ UPDATE:
 				// TODO We may want to find a more robust way of waiting for rollbacks to launch instead of
 				// just sleeping for 1 sec. If scheduling is slow, this will break update here instead of
 				// waiting for the (eventual) rollback
-				if rollback.ID == deploy.ID {
+				if rollback == nil || rollback.ID == deploy.ID {
 					break UPDATE
 				}