Fixing regression bug 246923. Bring back to life the fix for bug 13871, and improve on the fix for bug 246448. r=dveditz@cruzio.com, sr=darin@meer.net

docshell/base/nsDocShell.cpp

@@ -5500,7 +5500,10 @@ nsDocShell::GetCurrentDocumentOwner(nsISupports ** aOwner)
     }
 
     //-- Get the document's principal
-    *aOwner = document->GetPrincipal();
+    if (document) {
+        *aOwner = document->GetPrincipal();
+    }
+
     NS_IF_ADDREF(*aOwner);
 }