Don't show an empty branch field in the commit view

It's a little hack for issue 629, but don't resolve it.

src/IDF/templates/idf/source/commit.html

@@ -9,9 +9,9 @@
 <tr>
 <th><strong>{trans 'Author:'}</strong></th><td>{showuser $rcommit.get_author(), $request, $cobject.author}</td>
 </tr>
-<tr>
+{if $cobject.branch}<tr>
 <th><strong>{trans 'Branch:'}</strong></th><td>{$cobject.branch}</td>
-</tr>
+</tr>{/if}
 <tr>
 <th><strong>{trans 'Commit:'}</strong></th><td class="mono"><a href="{url 'IDF_Views_Source::treeBase', array($project.shortname, $commit)}" title="{trans 'View corresponding source tree'}">{$cobject.commit}</a></td>
 </tr>