Add default title for untitled tabs to shell devtools discovery page

content/shell/shell_devtools_discovery_page.html

Index: content/shell/shell_devtools_discovery_page.html
diff --git a/content/shell/shell_devtools_discovery_page.html b/content/shell/shell_devtools_discovery_page.html
index 62bb583f299fccb6d47097e5776400e42085bfb6..e8a730a6917ca5508865573e0fb224e73d6c55ba 100644
--- a/content/shell/shell_devtools_discovery_page.html
+++ b/content/shell/shell_devtools_discovery_page.html
@@ -33,7 +33,10 @@ function appendItem(item_object) {
   }
 
   var text = document.createElement("div");
-  text.innerText = item_object.title;
+  if (item_object.title)
+    text.innerText = item_object.title;
+  else
+    text.innerText = "(untitled tab)";
   text.style.cssText = "background-image:url(" + item_object.faviconUrl + ")";
   frontend_ref.appendChild(text);