Documentation index empty, module index link results in error 404

[gerritholl]

Describe the bug

In the documentation on readthedocs, the link to the Module Index results in Error 404. The link to the Index works, but the index is empty.

To Reproduce

• Open a web browser of your choice;
• Navigate to https://pytroll-schedule.readthedocs.io/en/latest/;
• Scroll to the bottom of the page;
• Click on either “Index” or “Module Index”.

Expected behavior

• I expect that clicking on the anchor Index gives me a list of all help topics.
• I expect that clicking on the anchor Module Index gives me a list of all modules and their documentation pages.

Actual results

• Clicking on the anchor Index gives me a page that is empty apart from headers.
• Clicking on the anchor Module Index results in Error 404.

Additional context

There is a similar problem in trollflow2, see pytroll/trollflow2#95