UI will crash when create application without destination namespace

[eric4545]

Describe the bug
Showing blank page / UI crash after login.

To Reproduce
If we cannot reproduce, we cannot fix! Steps to reproduce the behavior:

1. Create guestbook.yaml with below content

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
spec:
  project: default
  source:
    repoURL: https://github.com/argoproj/argocd-example-apps.git
    targetRevision: HEAD
    path: guestbook
  destination:
    server: https://kubernetes.default.svc
    # namespace: guestbook

2. kubectl -n argocd apply -k guestbook
3. kubectl -n argocd port-forward svc/argocd-server 8000:443
4. login https://localhost:8000, Blank page will occur

Expected behavior
Expected applications page working properly

Screenshots
If applicable, add screenshots to help explain your problem.

Version

argocd: v1.0.1+5fe1447.dirty
  BuildDate: 2019-05-28T17:28:05Z
  GitCommit: 5fe1447b722716649143c63f9fc054886d5b111c
  GitTreeState: dirty
  GoVersion: go1.11.4
  Compiler: gc
  Platform: darwin/amd64
argocd-server: v1.0.1+5fe1447.dirty
  BuildDate: 2019-05-28T17:27:38Z
  GitCommit: 5fe1447b722716649143c63f9fc054886d5b111c
  GitTreeState: dirty
  GoVersion: go1.11.4
  Compiler: gc
  Platform: linux/amd64
  Ksonnet Version: 0.13.1

[alexec]

@alexmt @jessesuen would this be fixed by #1687

[alexmt]

@alexec #1687 won't help. It still will be possible to specify an empty string as a value and api server will drop the field during serialization to json. Sent PR with fix: #1713