Reasons for creating this PR

When visiting a concept page (e.g. https://test.dev.finto.fi/yso/en/page/p23406), opening the hierarchy in the sidebar creates a bug where the hierarchy button is not visible for the open top concept (e.g. objects).

Link to relevant issue(s), if any

• Part of Epic: Hierarchical View Sidebar Tab #1521

Description of the changes in this PR

• Set hasChildren property of the open top concept object correctly
• Fix typos

Known problems or uncertainties in this PR

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that show that the new code works, or tests are not relevant for this PR (e.g. only HTML/CSS changes)
• The PR doesn't reduce accessibility of the front-end code (e.g. tab focus, scaling to different resolutions, use of .sr-only class, color contrast)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)