Description:
While working on the feature for redirection to the default cluster, the code started depending on clusters list getter. This getter was crashing on the domain search page because domain at that point is empty.

The fix:
Return empty clusters list array if domain is missing.

Other changes:

• Unit test was added to make sure the clusters list getter would always return empty array its dependent getter returns null.
• after reading more through the code i tweaked the code for redirection to only set the cluster name in the route if the route actually has clusterName param in its definition. (this is not related to the error but can prevent some if the new routes are added that doesn't have clusterName param)