Mime icon has invalid path in some cases

[wohnlice]

plone.app.portlets.portlets.navigation uses getNavigationRoot from this package to create a src base for the icon. However this uses getPhysicalPath which is inappropriate for some sites.

For example we have the site https://portals.imsweb.com/demo-portal where the path in the ZMI is /db01/plone_demo. This results in the icon

<img class="mime-icon" href="https://portals.imsweb.com/demo-portal/test-folder/Plone-Help-Users.docx/view" src="/db01/plone_demo/++resource++mimetype.icons/docx.png">

The src path won't work in this domain. Is there a reason getNavigationRoot doesn't just return root.absolute_url()? If that can't be the case, the portlet should instead use getNavigationRootObject and use its URL instead of path, I think.

Plone 5.1.5