doc/template.html: event.toElement is non-standard, use event.target instead

Fixes expanding of navigation menu in firefox

Author: daurnimator

doc/template.html

@@ -96,7 +96,7 @@ <h3 class="date">$date$</h3>
     element.className = 'collapsible';
     element.setAttribute('state', 'collapsed');
     element.onclick = function(event) {
-      if (event.toElement != this) return;
+      if (event.target != this) return;
       if (this.getAttribute('state') == 'collapsed') {
         this.removeAttribute('state');
       } else {