problem on SUBMIT event in gtkhtml2

["Sergey V. Beloshitsky" <snowman ukrpost com ua>]

I have connected submit event to HtmlDocument * html_doc in this way:
        html_doc = html_document_new();
        g_signal_connect (G_OBJECT (html_doc), "submit",
                          G_CALLBACK(submit_cb), NULL);

And then a load my document with form into html_doc like this:
        void read_html(gint k)
        {
                ...
                fd = open (html_file, O_RDONLY);
                html_document_open_stream(html_doc, "text/html");
                html_document_write_stream(html_doc, ostr,n);
                html_document_close_stream(html_doc);
                close (fd);
                ...
        }       

My submit_cb function looks like this:
        int submit_cb(HtmlDocument * html_doc, gchar* method, gchar* url, gchar* 
        encoding)
        {
        ...
        }

But when i  press on submit button i receive such message:
        (db_graph2:2604): Gtk-CRITICAL **: file htmlboxembeddedbutton.c line 33 
        (html_box_embedded_button_clicked): assertion 'embedded->form!=NULL' 
        failed

What migth it be of? Or maybe someone know how to handle forms it 
htmldocuments using gtkhtml2?