Search is broken (as in: JS is broken)

[quasipedia]

Problem

On a freshly generated site, entering any term as a search query will bear a stuck "three dots blinking" and no results.

Procedure to reproduce the problem

conf.py

html_theme = 'sphinx_rtd_theme'
html_show_sourcelink = False
html_sourcelink_suffix = 'txt'

command

sphinx-build -b html -n -W -d _build/doctrees  doc _build/html

Error logs / results

I should add that I checked searchindex.js and the payload of Search.setIndex is a totally fine js object, that can be read, parsed and used in the console and on node.

The topmost file in the stack trace has:

          var suffix = DOCUMENTATION_OPTIONS.SOURCELINK_SUFFIX;
          $.ajax({url: DOCUMENTATION_OPTIONS.URL_ROOT + '_sources/' + item[5] + (item[5].slice(-suffix.length) === suffix ? '' : suffix),

Yet... the suffix seem to be undefined for some reason.

Expected results

To find document matching my query!

Environment info

• OS: Fedora 25 64 bit
• Python version: 3.5.2
• Sphinx version: 1.5.1

[tk0miya]

Same as #3203 .
Sorry, it is a bug of sphinx_rtd_theme.