Fixed various issues in older Chrome versions

popup.js

Index: popup.js
===================================================================
--- a/popup.js
+++ b/popup.js
@@ -32,50 +32,50 @@ function init()
   ext.windows.getLastFocused(function(win)
   {
     win.getActiveTab(function(tab)
     {
       if (!/^https?:\/\//.exec(tab.url))
         document.body.classList.add("local");
     });
   });
-  
+
   // Attach event listeners
   document.getElementById("enabled").addEventListener("click", toggleEnabled, false);
   document.getElementById("clickhide").addEventListener("click", activateClickHide, false);
   document.getElementById("clickhide-cancel").addEventListener("click", cancelClickHide, false);
   document.getElementById("options").addEventListener("click", function()
   {
     openOptions();
   }, false);
-  
+
   // Set up collapsing of menu items
   var collapsers = document.getElementsByClassName("collapse");
   for (var i = 0; i < collapsers.length; i++)
   {
     var collapser = collapsers[i];
     collapser.addEventListener("click", toggleCollapse, false);
     if (!Prefs[collapser.dataset.option])
       document.getElementById(collapser.dataset.collapsable).classList.add("collapsed");
   }
-  
+
   // Ask content script whether clickhide is active. If so, show cancel button.
   // If that isn't the case, ask background.html whether it has cached filters. If so,
   // ask the user whether she wants those filters.
   // Otherwise, we are in default state.
   ext.windows.getLastFocused(function(win)
   {
     win.getActiveTab(function(t)
     {
       tab = t;
       document.getElementById("enabled").classList.toggle("off", isWhitelisted(tab.url));
-      
+
       tab.sendMessage({type: "get-clickhide-state"}, function(response)
       {
-        document.body.classList.toggle("clickhide-active", response.active);
+        document.body.classList.toggle("clickhide-active", response && response.active);
       });
     });
   });
 }
 window.addEventListener("DOMContentLoaded", init, false);
 
 function toggleEnabled()
 {
@@ -100,25 +100,25 @@ function toggleEnabled()
     while (filter)
     {
       FilterStorage.removeFilter(filter);
       if (filter.subscriptions.length)
         filter.disabled = true;
       filter = isWhitelisted(tab.url);
     }
   }
-  
+
   refreshIconAndContextMenu(tab);
 }
 
 function activateClickHide()
 {
   document.body.classList.add("clickhide-active");
   tab.sendMessage({type: "clickhide-activate"});
-  
+
   // Close the popup after a few seconds, so user doesn't have to
   activateClickHide.timeout = window.setTimeout(window.close, 5000);
 }
 
 function cancelClickHide()
 {
   if (activateClickHide.timeout)
   {