fixup! Bug 23247: Communicating security expectations for .onion

Fix a TypeError in _hasCustomRoot.

After this fix opening the identity panel will not result in a JS error
anymore. However, the identity panel will not be accurate for Onion
sites anyway.

browser/base/content/browser-siteIdentity.js

@@ -807,7 +807,11 @@ var gIdentityHandler = {
    * built-in (returns false) or imported (returns true).
    */
   _hasCustomRoot() {
-    return !this._secInfo.isBuiltCertChainRootBuiltInRoot;
+    // HTTP Onion Sites are considered secure, but will not not have _secInfo.
+    // FIXME: Self-signed HTTPS Onion Sites are also deemed secure, but this
+    // function will return true for them, creating a warning about an exception
+    // that cannot be actually removed.
+    return !!this._secInfo && !this._secInfo.isBuiltCertChainRootBuiltInRoot;
   },
 
   /**