Freemarker template visibility is incorrect in template editor

If you first select an item without freemarker and then one with freemarker, then the (read-only) freemarker field is empty.
However, if you first select template with freemarker and the the one without, then the template erronously shows the freemarker of the previously selected.

Steps to reproduce (in gogreen-enterprise trunk):

• login as admin
• open english channel in channel manager
• click edit channel
• click "URL and Navigation Management" under cogwheel at the right
• click Templates in harmonica
• click common.comments item (with no freemarker)
• click base.header.ftl (with freemarker)
  Expected: freemarker text field displays contents of ftl
  Actual: field is empty
• click "English Website" in breadcrumb to return to the channel and reopen templates via "URL and Navigation Management".
• click base.header.ftl (with freemarker)
• click common.comments item (with no freemarker)
  Expected: freemarker text field is empty
  Actual: freemarker of base.header.ftl is displayed.

Issue does not depend on the value (true or false) of property hst.config.editor.lock.inherited.nodes of node hippo:configuration/hippo:frontend/cms/hippo-channel-manager/channel-manager-perspective.