Fix link to back Home in 404.html

Author: svekars

pytorch_sphinx_theme2/templates/404.html

@@ -94,7 +94,7 @@ <h2 class="error-404-subtitle">Page Not Found</h2>
             <p class="error-404-text">The page you are looking for might have been removed, had its name changed, or is
                 temporarily unavailable.</p>
             <div class="error-404-buttons">
-                <a href="{{ html_baseurl or '/' }}" class="btn btn-primary error-404-button">
+                <a href="{{ pathto(master_doc) }}" class="btn btn-primary error-404-button">
                     Back Home <i class="fa fa-arrow-right" aria-hidden="true"></i>
                 </a>
                 <a href="{{ theme_feedback_url|default('https://github.com/pytorch/pytorch') }}/issues/new?template=documentation.yml&labels=module:%20docs,broken-link"