Description of problem:
When there are migplans that are not ready, the UI cannot display the migration plans and shows an error in the browser's console

Version-Release number of selected component (if applicable):
MTC 1.5.0

How reproducible:
Always

Steps to Reproduce:
1. Create  migration plan

$ oc get migplan
NAME      READY     SOURCE    TARGET           STORAGE   AGE
tests     True      host      target-cluster   noobaa    1m


2. Edit the migration plan in order to close it. Add "spec.closed: true" to the migplan yaml info.

oc edit migplan <MIGPLANNAME>
...
spec:
  closed: true

3. The migration plan is in not-ready status now

$ oc get migplan
NAME      READY     SOURCE    TARGET           STORAGE   AGE
tests               host      target-cluster   noobaa    1m

4. Go to the UI and open the migration plans screen

Actual results:
The UI crashes and we can see this error in the browser's console

app.bundle.js:2 TypeError: Cannot read property 'metadata' of null
    at t.default (app.bundle.js:2)
    at ci (app.bundle.js:2)
    at Ui (app.bundle.js:2)
    at jr (app.bundle.js:2)
    at bs (app.bundle.js:2)
    at Ms (app.bundle.js:2)
    at Os (app.bundle.js:2)
    at hs (app.bundle.js:2)
    at app.bundle.js:2
    at t.unstable_runWithPriority (app.bundle.js:2)
ar @ app.bundle.js:2
app.bundle.js:2  action UPDATE_PLAN_LIST @ 17:01:27.139
app.bundle.js:2 TypeError: Cannot read property 'metadata' of null
    at t.default (app.bundle.js:2)
    at ci (app.bundle.js:2)
    at Ui (app.bundle.js:2)
    at jr (app.bundle.js:2)
    at bs (app.bundle.js:2)
    at Ms (app.bundle.js:2)
    at Os (app.bundle.js:2)
    at hs (app.bundle.js:2)
    at app.bundle.js:2
    at t.unstable_runWithPriority (app.bundle.js:2)
v @ app.bundle.js:2
app.bundle.js:2 The above error occurred in task A
    created by anonymous
    created by anonymous

Expected results:
The UI should be able to display not-ready migration plans without problems

Additional info: