Fix visual bug from excessive LIs being rendered around Category breadcrumbs (PR #2160)

The category breadcrumb template in templates/components/bread-crumbs.js.handlebars contains LI tag wrappers around the references to the category-drop component (components/categorydrop.component.js). However, the component is already a LI itself, so the browser receives a HTML sequence <li> <li>foo</li> </li> from the Ember buffer. The first LI tag is automatically closed by the browser, leading to the rendered structure being <li></li> <li>foo</li> .... This extra LI tag causes a visual issue, which by coincidence isn’t visible on the default theme. See screenshot below.


Commit message: Prevent rendering of excessive <li> wrapper around a category breadcrumb which already is a <li>.

The excessive <li> wrapper coming from the template is automatically closed by the browser during the HTML parsing step, causing an empty <li> being visible in the rendered source (preceding the first breadcrumb). This causes a visual bug when not using the default Discourse stylesheet, because the extra LI element pushes the content to the right and sometimes also renders an extra black pixel.


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