Made the bubble use the ext object from the background page instead of including ext/background.js

safari/ext/popup.js

-with (safari.extension.globalPage.contentWindow)
+(function()
 {
-  this.ext = ext;
-  this.TabMap = TabMap;
-}
+  // Safari will load the popover once, and then show it everytime the icon is
+  // clicked. While Chrome loads it everytime you click the icon. So in order to
+  // force the same behavior in Safari, we are going to reload the page of the
+  // bubble everytime it is shown.
+  safari.application.addEventListener("popover", function()
+  {
+    document.documentElement.style.display = "none";
+    document.location.reload();
+  }, true);
 
-// Safari will load the popover once, and then show it everytime the icon is
-// clicked. While Chrome loads it everytime you click the icon. So in order to
-// force the same behavior in Safari, we are going to reload the page of the
-// bubble everytime it is shown.
-safari.application.addEventListener("popover", function()
-{
-  document.documentElement.style.display = "none";
-  document.location.reload();
-}, true);
+  // import ext into the javascript context of the popover. This code might fail,
+  // when the background page isn't ready yet. So it is important to put it below
+  // the reloading code above.
+  var backgroundPage = safari.extension.globalPage.contentWindow;
+  window.ext = backgroundPage.ext;
+  window.TabMap = backgroundPage.TabMap;
+})();