bad looking "Contents:" from root document appears in navigation side bar with Alabaster theme

[jfbu]

Refs: https://github.com/sphinx-doc/sphinx/commit/075a8cfb8f85e25ebb4277f07bc8a051c228fd61#commitcomment-22329934

With this in conf.py,

html_theme = 'alabaster'

# refs: http://alabaster.readthedocs.io/en/latest/installation.html#sidebars
html_sidebars = {
    '**': [
        'about.html',
        'navigation.html',
        # 'relations.html', # hidden by alabaster css anyway
        'searchbox.html',
        # 'donate.html',
    ]
}

and dummy project populated on top of one created by sphinx-quickstart,

Welcome to a's documentation!
=============================

.. toctree::
   :maxdepth: 2
   :caption: Contents:

   bar1
   bar2
   bar3

Indices and tables
==================

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`

one gets bad looking "Contents:" in html sidebar (here with language set to French, but does not matter)

from the :caption: Contents: in index.rst.

Environment info

• OS: Mac
• Python version: 3.5.3
• Sphinx version: 1.6.2
• Alabaster theme: 0.7.10

[jfbu]

This issue appears to be still relevant at time of Alabaster 1.0.0 and Sphinx 8.0.x.