Description of problem:

In TP 1.3 operator with Triggers 0.10.x, Event listener has the ability to serve across the namespaces using  the new `namespaceSelector` field, which is not currently supported in the UI.

Prerequisites (if any, like setup, operators/versions):

Openshift pipelines operator - TP1.3

Steps to Reproduce

1. Create a namespace and an event listener using the below yamls.

apiVersion: v1
kind: Namespace
metadata:
  name: bar

eventlistener.yaml

apiVersion: triggers.tekton.dev/v1alpha1
kind: EventListener
metadata:
  name: listener-sel
  namespace: foo
spec:
  namespaceSelector:
    matchNames:
    - bar

Actual results:

UI is broken with a NPE

Expected results:

UI should not break with the latest event listener API changes.

Reproducibility (Always/Intermittent/Only Once):

Always

Build Details:

Additional info: