Search form not working on home page

On my home page (https://digi-tails.com/) the search block generates incorrect code:

<form action="http://digi-tails.com/" method="post" id="search-block-form" accept-charset="UTF-8">...

on every other page it generate code like this:

<form action="/contact" method="post" id="search-block-form" accept-charset="UTF-8">...

So for some reason on the home page it sets action = the non-secure full link where every other page has action = relative link. If you search from my home page it redirects to the non-secure http:// link and you get this error message:

The form has become outdated. Copy any unsaved work in the form below and then reload this page. - See more at: http://digi-tails.com/#sthash.dpEv8WvT.dpuf

Any ideas on how to fix this?