Accidentally removed footer and header, cant get it back

Hello, I was trying to remove the header and footer on one page with this string 

<style>
  .header, #footer-sections{
    display:none !important;
  }
</style>

I used code from add block on the footer section. Now I have no header or footer on any of my pages and no way to delete the code from the section. What can be done?

Select page id with your element selector to set style only on the page you want

Use the following extension to get the right page ID: Squarespace ID Finder

How to get Page id: http://recordit.co/qwnj09oNCa

Code you can apply

PageID .header,PageID #footer-sections{
  display:none !important;
}

First, you can access this link: yourdomain.com/config/safe

Replace yourdomain with your real domain, or built-in domain

(This link will disable all code in Editing Mode, then footer, header will appear again)

Next, you can remove Code Block from Footer

Next, to remove header/footer on one page >> Edit that page >> Add a Code Block at top of page > Use this code

<style>
  header#header, #footer-sections{
    display:none !important;
  }
</style>