fix a traceback when unbundling does not add any changesets
only run the hooks when some changesets has been added
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<a class="title" href="?cmd=changeset;node=#node#;style=gitweb"><span class="age">#date|age# ago</span>#desc|strip|firstline|escape#</a>
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<a href="?cmd=changeset;node=#node#;style=gitweb">changeset</a><br/>
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<i>#author|obfuscate# [#date|rfc822date#] rev #rev#</i><br/>
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#desc|strip|escape|addbreaks#
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