fix(cli): Fix local diff/sync of apps using cluster name (#4201)
fix(cli): Fix local diff/sync of apps using cluster name (#4201)

This fixes the cluster query when the application uses cluster name as destination:

```shell
$ argocd app diff guestbook --local=guestbook/
FATA[0010] rpc error: code = Internal desc = runtime error: invalid memory address or nil pointer dereference
```
argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd