bookmarks: guard against listing bookmarks on unsupported repos
This fixes clones and pulls from statichttprepository repos.
{header}
<title>{repo|escape}: error</title>
</head>
<body>
<div class="container">
<div class="menu">
<div class="logo">
<a href="http://mercurial.selenic.com/">
<img src="{staticurl}hglogo.png" width=75 height=90 border=0 alt="mercurial" /></a>
</div>
<ul>
<li><a href="{url}shortlog{sessionvars%urlparameter}">log</a></li>
<li><a href="{url}graph{sessionvars%urlparameter}">graph</a></li>
<li><a href="{url}tags{sessionvars%urlparameter}">tags</a></li>
<li><a href="{url}branches{sessionvars%urlparameter}">branches</a></li>
</ul>
</div>
<div class="main">
<h2><a href="{url}{sessionvars%urlparameter}">{repo|escape}</a></h2>
<h3>error</h3>
<form class="search" action="{url}log">
{sessionvars%hiddenformentry}
<p><input name="rev" id="search1" type="text" size="30"></p>
<div id="hint">find changesets by author, revision,
files, or words in the commit message</div>
</form>
<div class="description">
<p>
An error occurred while processing your request:
</p>
<p>
{error|escape}
</p>
</div>
</div>
</div>
{footer}