[UI] Users should not be allowed to click "Documents" section for scopes with '0' collections

Build: 7.0.0-3444

Scenario:

• Single node cluster
• Create couchbase bucket
• Create new scope "s1" and create collections only under "_default" collection
• Click on "Documents" link for scope "s1"

Observation:

Seeing "No bucket selected" error

Expectation:

Need to prevent users from entering into 'documents' section where there are no collections under it