404 response returned if versionHistory property is missing on handle

Discovered while implementing the migrator (WPM-847).

The mixin hippo:versionInfo adds two properties hippo:branches and hippo:versionHistory. The versionHistory property is optional so it does not have to be present. When it's absent for a document the HST returns a NOT FOUND error response and in the Channel manager you will see 404 NOT FOUND.

Reproduction (via migration).

• Start with hap version 12.2, create a project and add a document to the project
• stop tomcat, checkout campaigns feature branch
• start tomcat with repo.boostrap=true and repo.upgrade=true
• open the document and use "View" menu to see document in channel manager
  Expect: project version of document
  Actual: 404 NOT FOUND and an error log with stack trace.

Simple reproduction (with feature branch of hap)

• create project and add a document to the project
• in console delete hippo:versionHistory property from handle of document, save changes
• in use "View" menu to see document in channel manager
  Expect: project version of document
  Actual: 404 NOT FOUND and an error log with stack trace.