fix symbol browser (Valama)

Guanako.iter_symbol (project.guanako_project.root_symbol, (smb, depth) => {
                if (smb.name != null) {
                    TreeIter next;
                    if (depth == 1)
                        store.append (out next, null);
                    else
                        store.append (out next, iters[depth - 2]);
                    string typename = get_symbol_type_name(smb);
                    store.set (next, 0, smb.name,
                                     1, typename.up(1) + typename.substring(1),
                                     2, (uint) smb.access,
                                     3, get_pixbuf_for_symbol (smb),
                                     4, Markup.escape_text (Guanako.symbolsig_to_string (smb)),
                                     5, Markup.escape_text (Guanako.symbolsig_to_string (smb, null)),
                                     -1);
                    if (iters.length < depth)
                        iters += next;
                    else
                        iters[depth - 1] = next;
                    return Guanako.IterCallbackReturns.CONTINUE;
                }
                return Guanako.IterCallbackReturns.ABORT_BRANCH;
            });